How to use Zero Conditional

Learn about Zero Conditional in English grammar. Clear and simple explanation of meaning and use, with examples.

Keith Taylor

Quick reference

If + present simple + present simple

Zero conditional is used to talk about facts or situations which are always true.

  • If you heat water, eventually it boils.
  • If people don’t eat or drink, they die.

What is a conditional sentence?

Conditional sentences consist of two clauses, an independent clause and an adverb clause of condition.

Here’s an independent clause:

  • Water boils.

And here’s an adverb clause of condition:

  • If you heat water

Adverb clauses are a type of dependent clause. Dependent clauses don’t make sense on their own. We need to join them to an independent clause for them to make sense. Let’s do that with this one::

  • If you heat water, it boils.

(We’ve replaced the noun “water” in the independent clause with the pronoun “it”, to avoid repetition.)

We’ve joined together the two clauses to make a conditional sentence. Conditional sentences tell us that something will or might happen (some kind of result or consequence) if a certain condition is met.

The adverb clause “If you heat water” gives us the condition, and the independent clause “it boils” gives us the result or consequence.

There are different ways we can put together conditional sentences, depending on whether we want to talk about conditions that are likely, unlikely or impossible to be met, results that are certain or just likely, and depending on whether we’re talking about the past, the present or the future.

One of these is what we call zero conditional.

Zero conditional form

We form zero conditional with the present tense in both the condition clause and the result clause:

Condition Result
If you put ice in the sun it melts.
If + present tense + present tense

Zero conditional meaning

So what can we say about the sentence above? Well, first of all, there is a real possibility of the condition being met. There is nothing to stop us putting ice in the sun. What about the result? Well, in the event that the condition is met, it is always true that ice melts, and so we can say that the result is certain.

And so that gives us the meaning of zero conditional sentences. We use them when the result of a real condition is always true or is a fact. Because of this we often use it for things like scientific laws. Here are some more examples:

  • If you heat water to 100 degrees, it boils.
  • If I eat too much, I get sick.
  • If I am lost I look at a map.
  • If you call to the dog, he comes.

Zero conditional additional points

Using present continuous and modal verbs in zero conditional

All of the examples above use present simple in both clauses. We’re not limited to this though. In the condition clause we can use present continuous:

  • If I’m driving, I don’t talk on my phone.
  • If I’m working, my boss is happy.

We can also use modal verbs in the result clause.

  • If I don’t wear my glasses I can’t see.

Other clause markers in zero conditional

A clause marker is a word which introduces a dependent clause. The most common clause marker we use in conditional sentences is “if”, but it isn’t the only one we can use. Have a look at these zero conditional sentences:

  • Unless I wear my glasses, I can’t see.
  • Unless you keep ice away from the sun, it melts.

“Unless” has the meaning of “if not”, and so with a little restructuring of the condition clause (changing “I don’t wear my glasses” to “I wear my glasses”) we end up with the same meaning as when we used “if”. Now have a look at these pairs of sentences:

  • If I’m happy, I smile.
  • When I’m happy, I smile.
  • If I do sport I feel relaxed.
  • When I do sport I feel relaxed.

Because zero conditional sentences tell us about results that are always true, it can sometimes sound more natural to use “when” rather than “if”.

Order of clauses in zero conditional

We can put the two clauses in either order in zero conditional sentences:

  • If you heat water, it boils.
  • Water boils if you heat it.

Related grammar points

First conditional
Second conditional
Third conditional

Keith Taylor

Keith is the co-founder of Eslbase and School of TEFL. He's been a teacher and teacher trainer for over 20 years, in Indonesia, Australia, Morocco, Spain, Italy, Poland, France and now in the UK.

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  • Henny Anggraini

    I teach zero conditional through song. Rain by The Beatles is an appropriate song for this. First, I ask my students to complete the lyrics while listening then we sing it together and after i write the zero conditional sentences from the lyrics on the board and highlight the use of zero conditional.

  • Mohamed Najih

    I like to introduce this simple structure by talking about general and scientific facts at the beginning of the lesson. Later on, I get them to think about possible relationships. For instance, “when it rains, the streets get wet”. I ask them: “what happens if it rains?” and at this stage I insist on using complete sentences to let them practice the structure.

  • Karen

    I introduce it with a story:

    “When it rains, my roof leaks. When my roof leaks, the walls get wet. When the walls get wet, they get moldy. When they get moldy, I get sick. When I get sick, I go to the doctor. When I go the doctor, he always says the same thing, “Fix your roof!”

    I repeat the story substituting ‘whenever’, ‘every time’ and ‘if’. They guess the rule and I write it on the board. I present examples of other uses, scientific truths etc. and this is followed by multiple choice sentence practice, a cloze activity and writing their own little story.

    And just as a reminder, I point it out to them whenever it comes up in texts and recycle it for comparative purposes when doing conditionals 1,2 and 3. After studying all 4 conditionals, I give them a type recognition activity – a long reading filled with 30 conditionals.

    • Suman Banik

      Thank you Karen. I like your story. I am thinking to use it in my class as well.

    • Jonathan Saldivia

      I just wanted to say that I’m amazed with the activity you’ve proposed for teaching this topic. I just found it great!
      Thanks for sharing.

      Jonathan S.

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