We use conditional tenses to speculate about what will happen, what would happen, what would have happened + if .and so on. Many conditional forms in English are used in sentences that include verbs in one of the past tenses. This usage is referred to as "the unreal past" because we use a past tense but we are not actually referring to something that happened in the past. There are five main ways of constructing conditional sentences in English. In all cases, these sentences are made up of an if clause and a main clause. In many negative conditional sentences, there is an equivalent sentence construction using "unless" instead of "if".
The zero conditional
The zero conditional is used for when the time being referred to is now or always and the situation is real and possible. The zero conditional is often used to refer to general truths. The tense in both parts of the sentence is the simple present. In zero conditional sentences, the word "if" can usually be replaced by the word "when" without changing the meaning.
If + simple present, simple present
If this thing happens, that thing happens.
If you don't send the report, we can't see the results.
If we call a meeting, people attend.
The 1st Conditional (or Future Conditional)
The 1st conditional is used to refer to the present or future where the situation is real. The 1st conditional refers to a possible condition and its probable result. In these sentences the if clause is in the simple present, and the main clause is in the simple future.
If + simple present, simple future
If this thing happens, that thing will happen.
If you don't apply for the job, you will miss the opportunity.
If we pull off the deal today, we will celebrate.
The 2nd Conditional (or Present Conditional)
The 2nd conditional is used to refer to a time that is now or any time, and a situation that is unreal. These sentences are not based on facts or truths. The 2nd conditional is used to refer to a hypothetical condition and its probable result. The 2nd conditional sentences, the if clause uses the simple past, and the main clause uses would + simple present.
If + simple past, would + simple present
If this thing happened, that thing would happen.
(but I'm not sure this thing will happen)
If she didn't beat around the bush, we would know what she wants.
If we got to the office late, we would have to catch up on work.
If I spoke more languages, I would work internationally.
The 3rd Conditional (or Past Conditional)
The 3rd Conditional is used to refer to a time in the past, and a situation that is opposite to reality. The 3rd Conditional is used to refer to an unreal past condition and its probable past result. In the 3rd Conditional sentences, the if clause uses the past perfect, and the main clause uses would + have + past participle.
If + past perfect perfect, would + have + past participle.
If this thing had happened, that thing would have happened.
(but neither of those things really happened)
If you had missed the deadline, you would have let the team down.
If it had rained, you would have gotten wet.
If I had accepted that promotion I would have been working in Vienna.
Mixed type conditional
The mixed type conditional is used to refer to a time that is in the past, and a situation that is ongoing into the present.
The facts they are based on are the opposite of what is expressed.
The mixed type conditional is used to refer to an unreal past condition and its probable result in the present. In mixed type conditional sentences, the if clause uses the past perfect, and the main clause uses the present conditional.
If + past perfect, would + present simple.
If this thing had happened, that thing would happen.
(but this thing didn't happen so that thing isn't happening)
If I had worked harder at school,I would have a better job now.
If we had looked at the map, we wouldn't be lost.
If you weren't interested in the role, you wouldn't have applied for the position.
Let's test yourself: (don't peep at the answers)
1. Would the company be still running if it ............made a big loss?
(make/ will make/ made)
2. If you ...........the figures on the balance sheet correctly, you get a correct total. (calculate/calculated/ have calculated)
3. If I .......... before making the decision, I would never have done it. (knew/know/had known)
4. Unless you .......... things easy, you'll get stressed out. (take/don't take)
5. ........ there was a problem, I'd have come into the office immediately. (Were I to know/Had I known/ If I knew)
Answer key
1.Made
2.Calculate
3.Had known
4.Take
5.Had I known
Now it’s your turn, write some examples below to help you start off your practice, I'll check them after ☺