1. Conditional Sentences If vs Unless
* When and How to use them *

2. Conditional sentences have two parts: Cause Effect / Action
Both If and Unless are possible.
There are four kinds of conditional sentences. One of them is an exception (type 0).
If-clause / unless
Every type is composed of
Main-clause
It doesn’t matter which comes first:
I’ll get a good mark, if I learn my vocabulary.
If I learn my vocabulary, I’ll get a good mark.
Introduction
Luis 1/2

3. If you freeze water, it becomes a solid.
If-clause
Simple present
Main-clause
If you freeze water, it becomes a solid.
Plants die, if you don’t water them.
If you mix blue and yellow, you get green.
It comes from oral language and it has a very definite meaning;
In this conditional, the time is now or always;
This type of sentence implies that the situation is real, possible or inevitable.
Type 0
Ritz 1/2

4. If-clause – Present Simple
Main-clause – Future (Will + Infinitive)
If I learn my vocabulary, I`ll get a good mark.
The if-clause usually indicates a real or possible situation that can happen in the present or in the future.
It is possible and also very probable that the condition will be fulfilled.
Type I
Ritz 2/2

5. If-clause – Past simple Main-clause – Conditional (Would + Infinitive) If I learnt my vocabulary, I would get a good mark. Type II is used when a condition is less probable to happen than in Type I Example: Will Mary be in time if she gets the ten o’clock bus? (Type I) No, but she would be in time if she got the nine bus. (Type II)
Type II
Ritinha 1/2

6. When we don’t expect the action in the if-clause to take place:
Example:
If burglar came into my room at night, I would throw something at him. (Meaning, I don´t expect a burglar to come in.)
When the supposition is contrary to known facts:
If I had a map, I would lend it to you.
(But I haven’t got a map. )
It is possible but very unlikely, that the condition will be fulfilled.
Type II
Ritinha 2/2

7. If-clause – Past perfect
Main-clause – Conditional Perfect [would (not) have + past participle]
If I had known that you were coming, I would have met you at the airport. (But I didn’t know so I didn’t went.)
NOTE: Both would and had can be contracted to ‘d.
You never use would in the IF-clause.
Example:
“If I’d known” “If I had known“,
“I’d have baked” “I would have baked..”
It is impossible that the condition will ever be fulfilled because it refers to the past.
Type III
Luis 2/2

8. It is used to emphasize an idea or action.
Unless means the same as if … not. Like if, it is followed by a present , a past or a past perfect tense. It is used instead of if + not in conditional tenses of all types:
It is used to emphasize an idea or action.
Type I (Unless + Present Simple)
You will never understand English, unless you study this grammar carefully. (= You will never understand English if you don’t study this grammar carefully)
Unless
Explicar se necessário o ênfase. Eu

9. Type II (Unless + Past Simple)
Unless he was very hill, he would be at work. (= If he wasn’t very hill, he would be at work)
Type III (Unless + Past Perfect)
I wouldn’t have phoned him, unless you had suggested it. (= I wouldn’t have phoned him, if you hadn’t suggested it)
Unless
Your Teacher: António Andrade