Conditional Clauses

Definition

Conditional clauses are adverb clauses that are used to talk about cause and effect (what always happens under certain conditions), future predictions (what will happen under certain conditions), and hypotheses (what might happen, or would have happened, under other conditions). Most conditional clauses start with the subordinating conjunction if, although sometimes we use when and unless. Like all dependent clauses, conditional clauses require a main clause, which expresses the result or outcome.

Discovery

Which sentences describe real situations (events and states that really happened)?

Which sentences describe unreal situations (events and states that did not really happen)?

Form

As you saw in the Discovery task, we can divide conditional clauses into real and unreal conditions, which mostly affects the verbs. The basic pattern of verbs is as follows. Note that in actual use, the if clause can be placed at the start or end of the sentence, that is, before or after the main clause. For clarity, the if clause is usually presented first in grammar tables, like this one:

One way in which conditional clauses are especially challenging for multilingual learners of English is that the past tenses in conditional sentences usually have nothing to do with past time. For example:

If it were sunny, I’d go for a walk after school. (This is future time, but it’s not real)

If school started later, my students would be less tired. (Now! This is present time, but it’s not real)

If we had grown our own tomatoes, we would have enjoyed them all summer. (This is an imagined past with present/future results.)

Note that in informal contexts especially in speech, we use would in the if clause, but this usage is considered incorrect in formal writing:

If the rain would clear, you could see the lighthouse. (In written/prescriptive English: If the rain cleared, you could see the lighthouse.)

Function

We can distinguish four main functions of conditional clauses. These are known in some grammar books as the four “levels” of the conditional (zero, first, second, third). The functional labels below are more descriptive, though. You will find a lot of conditionals in texts that Explain but sometimes also to Narrate, Inform, or Argue.

REAL: Generic, Habitual, and Inferential Conditional Sentences (“zero” conditionals)

These conditional sentences describe facts and habits. They can sometimes be used to make a confident inference based on the evidence in front of you. They are quite common in scientific writing and in math word problems. You can substitute when or whenever to talk about facts and habits.

If/When/Whenever clouds rise over mountains, precipitation falls. (unchanging facts; common in science writing)

If/When/Whenever I forget my umbrella, it rains. (habitual actions, past or present; common in conversation)

If Jiyoon has two apples and Salman has three apples, how many apples do they have together? (inference: the condition contains the math problem, and the main clause tells the student what kind of solution is needed)

If smoking can be banned in English pubs, it can be banned anywhere. (inference – since the “if” clause is true, the result clause can be inferred; note that we use a wide range of tenses or modal verbs for this function)

REAL: Future, or Predictive, Conditional Sentences (“first” conditionals)

Other real conditionals make predictions about the future. In these sentences, the condition is quite likely to happen.

If it rains, I will stay home. (a prediction that leaves no room for doubt)

If you give a mouse a cookie, he’s going to want a glass of milk. (confident prediction – this is a joke because you should never feed mice, but the sequence of events in this children’s story is presented as inevitable: one thing will lead to another)

If it rains, I should/may/might stay home. (the three modals express gradually weaker predictions)

If a company wants to do business in China, they (will) have to form a joint venture with a local company. (a real example, but the company is vague – any company)

UNREAL: Hypothetical Conditional Sentences (“second” conditionals)

Unreal conditionals imagine a situation that is not real at the moment. Sometimes the future is hypothetical, meaning it is possible but unlikely. The main clause then tells us what would happen in this unreal situation. Math word problems are sometimes written in this form.

If I had more time, I would (I’d) write a shorter letter. (this isn’t real – I don’t have more time – but it could be, and in that case, I’d write a shorter letter, so this is a present hypothetical. It’s also a line by the French philosopher Pascal.)

Carlos can build a shed in one day less than Juan. Together it would take them 10 days. How long would it take if they worked alone? (this is unreal – Carlos and Juan presumably always work together, but the math problem asks the student to create an equation for an imagined situation. The “if” clause is the condition, and the main clause tells them what to solve.)

For example, if you wanted to play the saxophone, you would first learn the clarinet. (a hypothetical example: I’m assuming you don’t really want to play the sax, but it’s possible you would, in which case, you would first need to learn the clarinet)

UNREAL Counterfactual Conditional Sentences (“third” conditional)

The last type of conditional is the least common and most complicated. In counterfactual sentences, we consider a situation that didn’t happen in the past and project what would have happened in another reality.

If you had finished your classwork, you wouldn’t have had any homework. (you didn’t finish your classwork in reality, so you really do have homework!)

If Shakespeare had been alive in the 18th century, he would/might/could have seen women playing his great female roles. (This counterfactual because we know Shakespeare died in 1616, but we can imagine what would have happened at a point in our past, the 18th century, when women were allowed to perform on stage.)

(Adapted in part from Celce-Murcia & Larsen Freeman, 1999, p. 548-552; Yule, 1998, p. 134-140)