Hello dear friends! If you decide to study conditional sentences, I can say that this is an excellent idea, since conditional sentences in English language have certain nuances that need to be understood and assimilated. There is a huge amount of grammatical material on this topic, it is chaotically fragmented and seems impossible to remember. This section of grammar is not that difficult. Forward!
Compound sentences in English By the name, you can understand that a complex sentence is made up of some parts. These parts are two or even several simple sentences, which by themselves may be incomprehensible, but taken together create a single semantic whole.
There are two types in total:
- compound proposal: all its parts can be torn apart, and each can exist independently. The same cannot be said for other types of proposals.
- complex sentence: its parts are interconnected through conjunctions and allied words. What does interconnected mean? This means that if one (main) is removed, the second cannot exist independently: it is, as it were, subordinate to the first.
Components of a conditional sentence We will analyze one of the types of complex sentences - conditional.
Often it is conditionals that seem to be such an insurmountable barrier for newcomers to the English language. We can give the following scheme for constructing this type of proposal:
In a conditional sentence, the subordinate clause is a subordinate clause, it indicates the condition and contains the union -if (if) or its analogues, in the main clause the result of the condition is proclaimed
Types of conditional sentences in English grammar
In different sources, you can find a different number of types and subtypes of conditional sentences: somewhere there are three of them, somewhere more. Many schemes are confusing. I believe that the classification, which includes four types, will be clearer to you. So, let's deal with all these types.
Conditional Zero/ Type 0 (Commontrue)
General truth is generally known facts, laws, etc. That is, in sentences of this kind we express general truths. 
Conditional Zero/ Type 0 (Common true) For example:
- If I do exercise, I become healthier. - When I exercise, I get healthier
Captain Obvious, by the way, always prefers this type ...
1 st Conditional / Type 1(Realreal)
The present real is understood as a real or probable reality that can occur both at the moment (the moment of speech) and in the future (usually the nearest). 
1st Conditional / Type 1(Real Real)
- If I write a novel, our things will get better. — If I write a novel, our business will go better.
Please note: in the Russian translation, the future is used in the subordinate clause. In the English clause, this tense is never used. V this example it can be considered conditionally real, in the sense: I am writing now, and when I finish it, everything will go better.
2 ndConditional /Type 2 (Unreal present)
Conditional sentences of the second type express unlikely or unrealistic situations, the possibility of translating them into reality is practically non-existent. uh 
2nd Conditional / Type 2 (Unreal present) Conditional mood is subjunctive mood. The subjunctive mood is formed using should or would, meaning corresponding to our particle -by.
Which auxiliary verb to use depends on the person
- 1st l. - should/would
- 2nd and 3rd - would.
Example:
- If I won the prize, I would build three-storeyed house. — If I won a prize, I would build a three-story house.
This type has a subtype - unlikely present (the event is unlikely, but still possible). In this case, we use Subjunctive in the subordinate clause, and Future Indefinite in the main clause. Let's rewrite the above sentence:
- If I'd win the prize, I'll build three-storeyed house. If I win a prize, I will build a three-story house.
It is necessary to feel the shades: in this phrase, a faint hope is felt.
3rd Conditional/ Type 3 (Unrealpast)
Conditional sentences of this type are used if the condition for doing something has become absolutely impossible, and one can only regret the missed opportunity in the past, such as: if I did something, if I were there ... then it would be - so-and-so... That is, type 3 is just an imaginary (unreal) past. 
3rd Conditional/ Type 3 (Unreal Past) Example:
- If they had gone in this trip, they would fall concert. - If they went on this trip, they would get to the concert.
In this type, too, there is a subtype of ... how to put it more accurately ... a lesser degree of unreality. If the condition with a stretch can still be called at least somehow feasible, then the simple past (or Subjunctive I / Past Subjunctive) is used in the subordinate clause.
- If I knew idioms, I'd speak English better. - If I knew idioms, then I would better speak English (the simple past is used in the subordinate clause).
For a more holistic perception of all of the above, I propose the following table, where all 4 types are collected, indicating which tenses should be used in each type.
Conditional sentences of mixed types (Mixed Conditionals)
Conditional sentences are not limited to these four types, there are also mixed conditionals. Usually, the second type and the third type are mixed.
I propose a simple exercise to reinforce. In this exercise, you need to make the correct conditional sentences by connecting their corresponding parts. At the end of the article you will find the keys to self-examination.
If ... Past Perfect ..., ... would have + past participle...
or
… would have + past participle... if ... Past Perfect ...
Use
Conditional sentences of the third type in English describe events in the past that could have happened but did not. Please note that these sentences are translated into Russian in the subjunctive mood, with the particle "by".
For instance:
If you had invited them, they would have come.
If you invited them, they would come. (But you didn't invite them, and that's why they didn't come.)
If you had worked harder, you would have passed the exam.
If you more was engaged, you would pass exam. ( But you did not study, and therefore did not pass the exam.)
If I had won that award, my life would have changed.
If I am won this award, my life would change.
If she had studied science, she would have found a better job.
If she studied science, she would have found the best job.
Other forms of conditional sentences of the third type
Using Modal Verbs in a Result Sentence
Instead of would have verbs can be used could have, might have, should have, and etc.
For instance:
If he had known, he could have helped you.
If he knew, he could you help.
You might have finished assignment on time, if you had planned more carefully.
You, maybe, would have fulfilled task on time if you planned more and more carefully.
If you hadn't prepared, you should have told the professor.
If you not prepared, then you should have said about it to the professor.
Using but for
Instead of if not expression can be used but for followed by a noun. This expression is usually used in formal speech.
For instance:
But for our savings, we wouldn't have been able to make the payments.
If not our savings, we would not be able to make payments.
There are four main types of "if" sentences in English:
There are four main types of sentences in English. "if":
1.The "zero" conditional, where the tense in both parts of the sentence is the simple present:
1. "Null" conditional, when both in the main and in the subordinate clauses the same time - simple present:
now or always and the situation is real and possible. They are often used to refer to general truths.
now or always, and the situation real and possible. Often such sentences mean general truths.
2. The Type 1 conditional, where the tense in the "if clause is the simple present simple future
2. Conditional type 1, when in a subordinate clause with "if" the verb is in simple present simple future
In these sentences, the time is the present or future and the situation is real. They refer to a possible condition and its probable result.
In these sentences, time is now or in the future, but the situation real. They talk about possible condition and likely outcome.
3. The Type 2 conditional, where the tense in the "if" clause is the simple past, and the tense in the main clause is the present conditional.
3. Conditional type 2, where in the subordinate clause with "if" verb in simple past tense, and in the main clause - in this conditional
In these sentences, the time is now or any time, and the situation is unreal. They are not based on fact, and they refer to an unlikely or hypothetical condition and its probable result .
In these sentences, time is now or any other time, and the situation unreal. These sentences do not reflect facts, they speak of an unlikely or hypothetical condition and its likely outcome
4. The Type 3 conditional, where the tense in the "if" clause is the past perfect, and the tense in the main clause is the perfect conditional.
4. Conditional type 3, where in the subordinate clause with "if" the verb is in past perfect time, and in the main clause - in perfect conditional.
In these sentences, the time is past, and the situation is contrary to reality. The facts they are based on are the opposite of what is expressed, and they refer to an unreal past condition and its probable past result.
In these sentences, the time past, and the situation contrary to reality. Facts real completely different, and the meaning of the sentence is that some unfinished business with the past could have something like this likely outcome in the past.
A further type of "if" sentence exists, where Type 2 and Type 3 are mixed. The tense in the "if" clause is the past perfect, and the tense in the main clause is the present conditional.
There is another type of offer with "if", where mixed types 2 and 3. In the subordinate clause with "if" the verb is in the past perfect, and in the main clause - in the present conditional.
In these sentences, the time is past in the "if" clause, and present in the main clause. They refer to an unreal past condition and its probable result in the present .
In these sentences, the time past in if-subordinate and the present in the main sentence. These sentences describe unreal condition in the past and his likely results in the present
Conditional sentences ( Conditional Sentences ) is the topic of more than one lesson.Conditionals in Englishdivided into different types, and each of them has its own rules of formation and use.
It takes a lot of practice to get comfortable with all types of conditional sentences. But first, you need to sort through what each type of Conditionals looks like and in what cases they are used. To do this, we have disassembled the rulesGrammar Conditionals in English, collected examples for each case and formed for all Conditionals table . Memorize constructions, repeat the differences between types and practice!
Structure of conditional sentences
Conditional sentences consist of two parts: the condition itself (air conditioning in english) and the consequences of fulfilling this condition (the main part of the sentence). The consequence states the action to be taken if the condition is met. It is also possible to determine what value each part has by a formal sign: the condition most often begins with the word if - if.
The two parts of a sentence can follow in any order: first you can say the condition, then the consequence, or vice versa. The order does not affect the meaning of the message. However, a syntactic rule appears here: the order affects the placement of a comma in a sentence. If the condition comes first in the sentence, then it is separated by a comma. If there is a consequence at the beginning, then a comma is not needed.
I will tell Gordon about it if I see him tomorrow - I will tell Gordon about it if I see him tomorrow.
Part with if condition is a subordinate sentence, therefore questions in such constructions are asked to the main part of the sentence, that is, to the consequence.
Will you tell Gordon about it if you see him tomorrow? Will you tell Gordon about this if you see him tomorrow?
Types of conditional sentences
There are 5 types of conditional sentences in English. They differ in the nature of the conditions in the sentence and the correlation of the event with reality and are formed using different grammatical rules.
English Conditionals :
- Zero Conditional - Zero type of conditional sentence
- First Conditional - First type
- Second Conditional - Second type
- Third Conditional - Third type
- Mixed Conditional - Mixed type
The choice of one of these types is determined by two parameters. First, the speaker needs to determine whether the implementation of the situation is real, or whether the fulfillment of the condition is possible only in the unreal world. Second, determine the time for each part of the sentence. In conditional sentences, the time in the condition and the consequence are independent of each other and each is determined by the meaning of the situation.
For example, when it comes to a real condition, about the order of things in the world, then simple verb tenses are enough for constructions. When a sentence refers to unrealistic situations that do not occur in life, the subjunctive mood appears in the constructions. In this case, an unreal event may refer to the present and future or to the past.
Let's take a look at each typeconditional sentence in English with examples: the scheme of education and the contexts in which they are used.
Zero Conditional
Let's start our review of conditional sentences with Zero Conditional. In such constructions, the appearance of if minimally affects the grammatical form of the verb.Conditional null constructs appear in contexts where the message indicates general truths or a recognized state of affairs. Typical uses of these sentences are instructions, manuals, descriptions of laws.
The scheme for the formation of such proposals is the simplest. Most often, the verb here is put in the simple present tense in both parts of the sentence.Zero Conditional Examples:
If you take the ice out of the refrigerator, it melts - If you take the ice out of the refrigerator, it melts.
If you click on this icon, the dialogue box appears - If you click on this icon, a dialogue box appears.
If I wake up at 6 o'clock, I feel awful - If I wake up at 6 o'clock, I feel awful.
The typical verb form for Zero Conditional is Present Conditional . However, not only the Present Simple may appear here: other present tenses may be used to describe prescriptions or the established order of things. The choice of a specific form of the verb is determined by what stage of the event the speaker wants to highlight. For example, when it is necessary to emphasize the process of performing an action, the Continuous form appears:
If you are driving a car, you need to be very attentive - If you are driving a car, you need to be very attentive.
When it comes to the result, the Perfect form appears:
If you have heard an alarm, you should leave the place immediately - If you hear an alarm, you should leave the place immediately.
The main part of Zero Conditional often uses modal verbs: can (be able, be able) / may (be able, have permission) / should (should) / must (should). Modal verbs describe an action that is carried out with a certain degree of probability.
When we ask a question to sentences like Conditional 0 , you need to pay attention to which verb is used in the main part. If there is to be or modal verbs, then you need to move it to the first place in the sentence. If other forms are used, then you need to add the auxiliary verb do / does to the beginning of the question, and put the semantic verb in the infinitive.
Does the ice melt if I take it out of the refrigerator? Does ice melt when you take it out of the refrigerator?
Should I leave the place immediately if I have heard an alarm? - Do I need to leave the premises immediately if I hear an alarm?
Since the zero conditional is often used as advice or guidance, the verb in the main part can be in the imperative mood. The above examples Conditional Zero can be reformulated using the verb in the imperative mood:
If you are driving a car, be very attentive - If you are driving a car, be very attentive.
If you have heard an alarm, leave the place immediately - If you hear an alarm, leave the place immediately.
Mandatory Zero Conditional
Unlike the types 1, 2, 3 conditionals, in the zero type of conditional sentences, there is no element of assumption. They only state the facts that are happening and are binding. The union if in such constructions can be replaced with the union when (when).
When you take the ice out of the refrigerator, it melts - When you take the ice out of the refrigerator, it melts.
When you have heard an alarm, you should leave the place immediately
When you are driving a car, you need to be very attentive - When you are driving a car, you need to be very attentive.
When you click on this icon, the dialogue box appears - When you click on this icon, a dialogue box appears.
When I wake up at 6 o'clock, I feel awful - When I wake up at 6 o'clock, I feel awful.
Under zero condition ( zero condition ) you can also replace if with every time (each time), if the sentences describe habits and imply repetitive actions:
Every time I wake up at 6 o'clock, I feel awful - Every time I wake up at 6 o'clock, I feel awful.
First Conditional
In sentences with First Conditional, the role of the condition is more explicit. It contains an assumption about the course of events, and if it is fulfilled, then the action from the main part of the sentence is possible.
The construction of the first type refers to the future tense: if the condition occurs, then the consequence will occur. In this case, the probability of the event occurring is high. An example of this type of proposal is:
If I see Gordon tomorrow, I will tell him about it - If I see Gordon tomorrow, I will tell him about it.
First Conditional education includes present and future tenses. If is followed by Present, and in the consequence part by Future. Note that there is no future tense verb after if, despite the fact that the condition essentially describes an event that can only happen. In Russian, both parts of the sentence are most often translated in the future tense, and this often confuses English learners. It must be remembered that in English Future is placed only in part of the investigation.
I will pass the exam if I work hard - I will pass the exam if I work hard.
The essence of using conditional sentences of the first type is to communicate the likely course of events, but leaving the uncertainty that the situation will definitely happen. This distinguishesFirst and Zero Conditional rule. In sentences of the first type, the conjunction if cannot be replaced by when without changing the meaning.
If we try to put the union when in a familiar example, the meaning of the phrase will change. With the word when, the sentence takes on the connotation of the speaker's confidence that the event will happen.
When I see Gordon, I will tell him about it - When I see Gordon, I will tell him about it.
Despite the fact that the Present Simple in the conditional part of the sentence is the most common time for1st Conditional rules, other forms of the present tense are possible here. For example Present Continuous:
If she is sleeping, I will wake her up - If she is sleeping, I will wake her up.
All types of conditional sentences often use modal verbs. They replace will in the main part of the sentence.First Conditional Exampleswith modal verbs:
- can - can (has the ability): If we hurry up, we can catch the last train - If we hurry, we can catch the last train.
- may - can (allowed): If you finish all your work today, you may have a day off tomorrow - If you finish all your work today, you can take a day off tomorrow.
- should - should (should): If she wants to get this job, she should be ready to work hard - If she wants to get this job, she should be ready to work hard.
- must - must: If it rains, you must stay at home - If it rains, you must stay at home.
As in the zero type of conditional sentence, here it is possible to use imperative mood in the main part. Suchexamples of the First Conditional ruleis the same as the Zero Conditional type, and the difference in meaning is inferred from the context.
If you see her, send my regards - If you see her, say hello from me.
Second Conditional
The second type of conditional sentences in Englishdescribes unrealistic situations in the present or future time, the probability of which is very small.
Such constructions are characterized by a special verb form - the subjunctive mood. It can refer to the past, present or future. The Second Conditional expresses the meaning of present and future tenses.
In the subjunctive mood, we are talking about unrealistic situations that relate to the plan of our expectations, ideas, desires. IfZero and First Conditional rulereferred to real events, then this type of sentence characterizes the unreal world. In Russian, such a meaning is expressed by the particle “would”.
If I had a thousand years to live, I would become an expert in many areas - If I had lived a thousand years, I would become an expert in many areas.
This example is a typical conditional sentence Conditional II with an unrealistic situation. It is in terms of our dreams or expectations, but not in terms of reality: a person cannot live a thousand years.
Although, in the sense of the sentence of the second type, the conditions refer to the plan of the present or future tense, Conditional 2 rule instructs to put the verb in the past tense. The use of past forms is also characteristic of the Russian language:
If I lived in Italy, I wouldn't try to spend every holiday at the seaside - If I lived in Italy, I wouldn't try to spend every holiday at the seaside.
For Second Conditional ruleformation combines the past tense in the condition and the subjunctive mood in the consequence. In the conditional part, the verb is put in the Past Simple, and in the part of the consequence, the verb would appears, followed by the semantic verb in the infinitive without the particle to. A feature of these sentences is that the past tense of the verb to be in the condition is put in the form were, regardless of the number and person of the subject.
If I were a king, I would live in this palace - If I were a king, I would live in this palace (but I'm not a king and I'm unlikely to become one).
We would be friends if Carol were a little more optimistic - We would be friends if Carol were a little more optimistic.
Often the condition describes an event that is equivalent to both the future and the past, since we are talking about an imaginary world. In Russian, in such sentences, the form “be” is appropriate: If I were a king - Be I a king.
Unlike the Zero and First types,second condition in englishimplies that the condition is unlikely to be met. The difference between such situations can be demonstrated using an example from the first type of conditional sentences, if you change the verb forms in the statement:
If I saw Gordon, I would tell him about it - If I see Gordon, I will tell him about it.
In such an example, the speaker claims that the situation is very unlikely, and the meeting is more likely to be an unrealistic plan.
If I saw mister President on the street, I wouldn't know what to think - If I saw the president on the street, I wouldn't know what to think.
A typical situation in which the second conditional occurs is when we want to convey how we would act in the place of another person. There is no way we can become a different person, so the choice of an unrealistic conditional sentence is unambiguous. Often this wording is used as advice:
If I were you, I wouldn't behave like this - If I were you, I wouldn't behave like this.
In sentences of the second type, various modal verbs can replace the would form, but their forms are somewhat different from those previously discussed. Let's look atexamples Second Conditionalwith modal verbs:
- could - can: I could become a star if I were more lucky - I could become a star if I were more lucky.
- might - can: If we had more money, we might stop work - If we had more money, we could stop working.
- should - follows: If I had time, I should go to the gym - If I had time, I should go to the gym.
- must - must: I must be in school at this time of day if I were a child - At this time of the day I should be at school if I were a child.
Third Conditional
The construction of the third conditional also refers to the unreal plan. However, unlike the second type, we are talking here about the past tense. Often such sentences are used to convey regret about things done or not done, or to criticize past events.
If I had known it in advance, I wouldn't have said such things - If I had known about it in advance, I would not have said such things.
If in the case of the second typeconditions in Englishwe are talking only about supposed events, then from the construction of the third conditional sentence we learn that in reality the events did not develop as they are presented in the sentence.
The main part of the sentence is formed using the construction would have and the past participle. The verb in the condition is put in the past perfect form. The abbreviated form of the verb would is ‘d’, which is the same as the abbreviated form of the verb had.
If I had called him that day, we would have solved this problem = If I’d called him that day, we’d have solved this problem - If I had called him then, we would have solved this problem.
Build sentences of the third typeconditionals in Englishcan be in the form of inversion, that is, using the reverse word order. To do this, the union if is omitted in the condition, and the verb had is placed in the first position in the sentence:
Had I called him that day, we would have solved this problem - If I had called him then, we would have solved this problem.
Modal verbs in the Third Conditional have the same form as in the second type of sentences and replace the verb would in the main part of the phrase. As examples, we can consider the sentences already familiar to us, put in the third type of conditions:
- could - can (has the opportunity): If we had hurried up, we could have caught the last train - If we were in a hurry, we could catch the last train.
- might - can (allowed): If you had finished all your work, you may have had a day off today - If you finished all your work, you could take a day off today.
- should - should (should): If she had wanted to get this job, she should have been ready to work hard - If she wanted to get this job, she should have been ready to work hard.
- must - must: If it had rained, you must have stayed at home - If it started to rain, you should have stayed at home.
Mixed Conditional
The mixed type combines different types of conditional sentences. However, not all types participate in such constructions. conditions 0 1 2 3 but only the second and third.
In Mixed Conditional, one of the parts - the condition or the effect - refers to the past. The mixed type of conditional sentences can be divided into two types:
- a combination of Second Conditional in the condition and Third Conditional in the consequence.
- combination of Second Conditional in consequence and Third Conditional in condition.
We give examples for each case.
- If + Second Conditional / Third Conditional
If I were clever enough, I wouldn't have done this - If I were smart enough, I wouldn't have done it.
The Third Conditional contains the main part of the sentence that does not correspond to the real past (I wouldn't have done this - “I would not have done this”), and the condition is characterized by a situation that is also fair for the present (If I were clever enough - “If I were smarter ”, Second Conditional).
- If + Third Conditional / Second Conditional
If I had won that lottery, I would now live in France - If I won that lottery, I would now live in France.
In this sentence, the main part refers to the present (I would now live in France - “I would live in France now”), but the condition for its implementation is determined by the failed past (If I had won that lottery - “If I won that lottery ").
Conditions table
The subject of Conditionals is extensive and requires regular repetition of the material. To better understand the differences between the five types, we summarize intable of conditional sentences in English:
If ... Simple Present ..., ... Simple Future ...
or
Simple Future ... if ... Simple Present ...
Use
Conditional sentences of the first type in English describe future events. The situations described in such sentences are real and quite possible. Please note that in Russian such sentences have the future tense.
For instance:
If I see her, I will give her love.
If I am see her, me I will pass hello from you.
If you finish on time, you will go to the movies.
If you finish on time, then you go to the cinema.
The match will be canceled if it rains.
Match cancel, if it will rain.
You will be late if you don't hurry up.
You you'll be late, if you don't hurry.
I will buy a car if I get my rise.
I AM buy car, if to me raise salary.
Other forms of conditional sentences of the first type
Using only the future tense
Sometimes in both parts of the conditional sentence (both in the conditional clause and in the result clause) the future tense can be used. This usage is especially typical for polite requests.
For instance:
If you will marry me, I will love you forever.
If you on me get married, I am I will always you be in love. (Such an offer sounds more polite than If you marry me…
)
If you will wait for me, I will come with you.
If you me wait, I am I'll go with you.
If you will help us, we will be grateful.
If you to us help, we we will grateful.
To give an even greater shade of politeness, instead of a verb will in a conditional clause, you can use would.
For instance:
If you would help us, we will be extremely grateful.
If you to us help, we we will overly grateful.
If you would come this way, I will take you to the theatre.
If you pass here, I I'll take you you to the theatre.
The going to form in the sentence-result
Form going to often replaces the verb will in conditional sentences of the first type. This usage emphasizes the sentence-result.
For instance:
If you skip your classes, you are going to fail.
If you you will miss classes, you you won't pass exams.
If you don't mend your ways, you are going to land in trouble.
If you you won't get better, then you will get in trouble.
Also form going to can be used in a conditional sentence with the meaning "intend", "gather".
For instance:
If you are going to skip school, you certainly won't pass your exams.
If you gonna skip class, you don't you won't pass exams.
The present perfect tense in a conditional sentence
Sometimes in a conditional instead of tense simple present can be used present perfect. This usage emphasizes the completion of the action-condition. In Russian, this difference is not displayed in any way.
Compare:
We will go to the movies if you have finished your work. ( The action described in the condition is underlined.)
We will go to the movies if you finish your work. ( The action described in the condition is not underlined in any way.)
We let's go to to the cinema, if you finish work.
Using should in a conditional clause
Verb should can be used in a conditional clause to indicate that what is described in the conditional is possible but unlikely. As in the previous case, this difference cannot be traced in any way in Russian.
For instance:
If he should arrive, we will invite him along to the dinner.
If he will come, we let's invite him to have dinner with us. ( It is unlikely that he will come. But if he does come, we will invite him to dinner.)
Usage should in conditional sentences of the first type has a stronger connotation than the use of conditional sentences of the second type, where imaginary or unreal situations are described.
Compare:
If he arrives, we will invite him along to dinner.
If he will come, we let's invite him to have dinner with us. ( Conditional sentence of the first type - it is very likely that he will come.)
If he arrived, we would invite him to dinner.
If would he came, we would be invited him to have dinner with us. ( Conditional sentence of the second type - it is very likely that he will not come.)
If he studied, he would pass the exam.
If he prepared, he would pass exam. ( Conditional sentence of the second type - it is very likely that he will not pass the exam.)
If he studies, he will pass the exam.
If he will prepare, he will pass exam. ( Conditional sentence of the first type - it is very likely that it will be prepared. And if so, he will pass the exam.)
If he should study, he will pass the exam.
If he will prepare, he will pass exam. ( The first type of conditional using should is very likely not to be prepared. But if he does, he will pass the exam.)
use of happen to/should happen to
Expressions can sometimes be used in a conditional clause happen to, should happen to. This usage suggests that what is expressed in the condition is unlikely, but if it happens, then what is described in the result clause will happen.
For instance:
If they happen to come to town, we will meet them.
Happen like this, what they will come to the city, we meet. (It is unlikely that they will come. But if they come, we will meet them.)
Expression should happen to has the same meaning:
If he should happen to get stuck in that town will be able to find a good hotel.
Happen so that he will be stuck in this city, he will be able find a good hotel.
Using Modal Verbs in a Result Sentence
Modal verbs can be used in the result clause to describe a future opportunity, permission, advice, etc.
For instance:
If you finish your work, you can go out and play.
If you finish work, then you can go play outside.
You should see a doctor if you continue feel bad.
To you should go to the doctor, if you and beyond you will to feel yourself bad.
If I arrive early, I might give him a call.
If I am I will arrive early, i maybe, call him.
Use of conjunctions provided (that), as long as
Instead of union if unions can be used provided (that) and as long as to emphasize that in order for what is described in the result clause to happen, a certain condition must be met.
For instance:
Provided (that) he finishes his studies, he will find an excellent job. (= If he finishes his studies, he will find an excellent job.)
In case if he will finish training, he will find great job.
As long as you pay off the loan, the house will be yours at the end of this year. (= If you pay off the loan, the house will be yours at the end of this year.)
If you you pay loan, house will become yours by the end of this year.
