Conditional sentences in English: What are they and how to use them?

A conditional is a type of sentence that says that one situation depends on another. Because there are always two situations described, a conditional sentence always has two parts: a condition and a result. They are also known as “if-sentences,” because the part that describes the condition usually starts with “if,” for example:

To use conditional sentences in English, you will need to learn some special grammar because their structure shows the time frame for the condition and its consequences, as well as the probability that they will actually happen. Conditionals are commonly divided into four types (first, second, third, and zero conditionals), each with its own structure, so let’s unpack each of them in turn.

Conditional sentences usually consist of a conditional clauseNo definition set for clauseLorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. (an "if" clause) and a main clause (a "then" clause).

• A conditional clause sets a condition, which can be plausible (possible or likely to happen) or implausible (impossible, imaginary, or very unlikely to happen). A conditional clause is a type of dependent clauseNo definition set for dependent clauseLorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum., because it doesn’t really make full sense without a main clause.

• A main clause describes what happens as a result of the situation in the conditional clause. The condition may never be met, but if it is met, the main clause is the result

The conditional clause may come before, after, or (rarely) in the middle of the main clause.

When the main clause follows the if-clause, it can begin with then, which is why the main clause is sometimes called the “then-clause” and why conditional sentences are sometimes called if-then sentences.

The main clause may also be a question:

If is the most common word we use to introduce conditional clauses, but there are others, too. They are called “conjunctions of condition” and differ slightly in meaning and degree of formality

• provided / providing (that)

• so/as long as

• on condition that

• suppose / supposing

• unless

• in case

You can read more about how to use these conjunctions of condition in our post on English conditionals without if!

There are four main types of conditionals in English (zero, first, second, third) and a “mixed” type which has features of each. Each type of conditional is used in a different circumstance, depending on how plausible(possible, likely, real) or implausible(unlikely, impossible, imaginary) the condition is, and each has its own grammar.

Here is a summary of the grammar rules that usually go with each type of conditional:

Let’s look at each type in more detail!

Use a zero conditional to describe the result that always happens when the condition is true. The most typical structure for zero conditionals is:

Zero conditional sentences describe universal truths, such as scientific facts or typical/repeated personal situations. That is why we use the English present simple — because this is the tense we usually use for general truths.

In zero conditionals, if is very close in meaning to when or whenever:

Here are some more examples of zero conditionals in English:

• If a car moves at 55 mph, its braking distance is about 180 feet.

• If it snows a lot in this area, the roads are closed.

• What do we have to do if smoke detectors go off?

• If I don’t feel like cooking, I can always order pizza.

• If he sees a celebrity, he must ask for a selfie.

Use a first conditional to describe a result that will happen in one specific case when the condition is true. The condition here is always possible. A typical first conditional sentence looks like this:

First conditional sentences are used to talk about future events that depend on a “real” condition, that is, a condition which is still possible, but we just don’t know for certain that it will happen.

First conditionals are used for negotiating, discussing plans and back-up plans, giving advice and threats, making promises, and giving warnings.

Use a second conditional sentence to describe the imaginary result of an imaginary situation in the present or future. The most typical structure for the second conditional is

The most striking feature of the second conditional is that the tenses are all “back-shifted.” This means that, even though we are discussing an imaginary situation in the present or future:

• We use the past simple in the if-clause.

• We use would rather than will in the main clause.

Second conditional sentences describe imaginary situations in the present and in the future. The imaginary situation is sometimes technically possible, but you’re not really making a plan, it’s just a hypothetical discussion. The condition can, therefore, be called “unreal,” as the speaker thinks that the situation is unlikely or impossible, for example:

• If I bought a smaller house, I would spend less time cleaning!

  → It is technically possible for me to buy a small house in the future, but I do not really plan to move, so the situation is imaginary or speculative.

  
• 

  I wouldn’t ask you for cash if I were rich.

  → I am not rich. Someday, I might become rich, but that does not impact the situation now, so I am only imagining being rich. I am not making a plan.

Here are two common variations on the second conditional:

• It is possible to use past continuous after if too, as long as would is also followed by be + present participle (verb + -ing), for example:

  past continuous

  If I weren’t driving now, I would be watching the game.

• You can replace would in the main clause with other English modal verbs, especially could or might,

  • I might stay longer if I didn’t have a return ticket.

  • I could be a basketball star if I was a little taller.

Third conditional sentences are used to talk about missed opportunities in the past. The condition is always something that did not happen or is contrary to the past fact, and so the main clause describes a past that also didn’t happen. Third conditionals are used to talk about re-imagined history and biography, coincidences, regrets, or lucky escapes.

The basic structure for third conditional sentences is:

The tenses in the third conditional are “back-shifted” like the tenses in the second conditional, but because here we are talking about a past situation they are shifted to a further past by using the past perfect and would have + past participle:

• If he had eaten more, he would have had more energy.

  → He did not eat much, so he did not have energy.

• I would have gotten there on time if there hadn’t been an accident on the bridge.

  → There was an accident on the bridge, and I didn’t get there on time.

Some common variations on the third continuous:

• The past perfect continuous is also possible in the if-clause:

  I wouldn’t have won the contest if I hadn’t been practicing for days.

• Other modal verbs, such as could or might, can be used instead of would, and the past perfect continuous:

  If I had been there before, I might have known where to go.

The four types of conditional sentences described above are not isolated from each other. Instead, it’s possible to combine an if-clause of one type with a main clause of another type. For example:

• second conditional (past reference)zero conditional (present reference)

  If I misunderstood you and let everyone down that day, then I am truly sorry.

  → Condition: a past situation that is unlikely/imagined
  → Result: something that is always true now when the condition is met
  
• third conditional (past reference)second conditional (present reference)

  If she hadn’t brought extra socks, Johnny’s feet would be wet and dirty now.

  → Condition: a past situation that did not happen (she did bring socks)
  → Result: a situation in the present that is imagined
  
• third conditional (past reference)second conditional (present reference)

  You would have been fired if your manager weren’t so understanding.

  → Condition: a present situation that is imagined (your manager is understanding)
  → Result: a past situation that did not happen (you were not fired)
• second conditional (future reference)first conditional (future reference)

  If you would postpone the party until Sunday, I’ll definitely be there.

  → Condition: an imagined situation in the future
  → Result: a planned future situation
  

The most popular types to mix together are the second and the third conditionals, but virtually any combination of the four types is possible.

Conditional sentences consist of an if-clause and a main clause, and belong to one of the following types:

• Zero conditionals (present simple + present simple) talk about general truths.

• First conditionals (present simple + will) talk about “real” conditions and their consequences in future.

• Second conditionals (past simple + would + verb) talk about “unreal” conditions and their consequences in present and future.

• Third conditionals (past perfect + would have + past participle) talk about “unreal” conditions and their consequences in the past.

• Mixed conditionals (an if-clause of one type, a main clause of another type)

Try practicing conditional sentences in English with these English conditional sentences activities! Or, if you’d rather learn about some other ways to create conditional sentences without using the word if, have a look at our post on English conditionals without if!