Grammar 5 conditional sentences

If-Clauses Type I, 2 and 3

Conditional Sentences are also known as Conditional Clauses or If-clauses. They are used to express that the action in the main clause (without if) can only take place if a certain condition (in the clause with if) is fulfilled. There are three types of Conditional Sentences.

Conditional Sentence Type 0 (real condition)

They are used to express something that is always true.

Form: if + present simple + main clause: present simple

Example: If the sun shines, snow melts.

Conditional Sentence Type 1 (real condition)

→ It is possible and also very likely that the condition will be fulfilled.

Form: if + Present Simple, Present Continuous, Present Perfect, Present Perfect Continuous + main clause: will - Future, imperative, can, may, might, must, should + bare infinitive

Example: If I find her address, I’ll send her an invitation.

Conditional Sentence Type 2 (unreal condition)

→ It is possible but very unlikely, that the condition will be fulfilled.

Form: if + Past Simple, Past Continuous + main clause: Conditional I (= would, could, might) + bare infinitive

Example: If I found her address, I would send her an invitation.

Conditional Sentence Type 3 (unreal condition)

→ It is impossible that the condition will be fulfilled because it refers to the past.

Form: if + Past Perfect, Past Perfect Continuous + main clause: Conditional II ( = would / could / might + have + Past Participle – Perfect infinitive)

Example: If I had found her address, I would have sent her an invitation.

• We do not normally use will, would, should in an if-clause. However, we can use will or would after if to make a polite request or express insistence. We can use should after if to talk about something which is possible, but not very likely to happen.

E.g. a) If the weather is fine tomorrow, we will go camping.

b) If you will fill in this form, I’ll process your application. (Will you please fill in … – polite request)

c) If you will not stop shouting, you’ll have to leave. (If you insist on shouting… –- insistence)

d) If Tom should call, tell him I’ll be late. (We do not think that Tom is very likely to call)

• We can use unless instead of if … not in the if-clause of Type 1 conditionals. The verb is always in the affirmative after unless. E.g. Unless you leave now, you’ll miss the bus. (= If you don’t leave now, you’ll miss the bus.)

• We can use were instead of was in the if-clause of Type 2 conditionals. E.g. If Rich was / were here, we could have a party.

• We use If I were you when we want to give advice. E.g. If I were you, I wouldn’t complain about it.

• The following expressions can be used instead of if: provided/providing (that), as long as, supposing/suppose, in case, on condition (that), but for + -ing form/noun, even if, only if, otherwise, or else.

E.g. You can see Mr. Carter provided you have an appointment.

Suppose the boss came now, what would you say?

Get up now or else you’ll be late.

But for his advice, I wouldn’t be able to solve my problems.

Note that when only if begins a sentence, the subject and the verb of the main clause are inverted. E.g. Only if you have a ticket will you be allowed in.

• We can omit if in the if clause. When if is omitted, should (Type 1), were (Type 2), had (Type 3) and the subject are inverted.

E.g. Should Peter come, tell him to wait. (=If Peter should come,…)

Were I you, I wouldn’t trust him. (If I were you,…)

Had he known, he would have called. (=If he had known,…)