What is a zero conditional sentence?

It is a sentence that says what always happens when a condition is met, using the present simple in both clauses. The if-clause gives the condition and the main clause gives the automatic result: If you don't charge the phone, the battery dies. It is used for facts, general truths, habits, rules, and instructions rather than for predictions about one occasion.

What is the difference between the zero conditional and the first conditional?

The zero conditional describes a result that follows every time, so both clauses use the present simple: If it rains, the garden floods. The first conditional predicts the result of one real future possibility, so the main clause uses will: If it rains tomorrow, the garden will flood. The if-clause looks the same in both; the tense of the result clause and the meaning differ.

Can I use when instead of if in the zero conditional?

Yes, and the meaning does not change, because the result is guaranteed either way. If I eat too late, I sleep badly and When I eat too late, I sleep badly are the same sentence. Whenever and every time work as well. The two words only separate in the first conditional, where if leaves the event uncertain and when treats it as sure to happen.

Can the zero conditional have an imperative?

Yes, and this is how English gives conditional instructions. The condition stays in the present simple and the result becomes a command: If the alarm goes off, leave the building. If you feel unwell, stop and rest. The negative imperative works the same way: If the oil smokes, don't add the food.

Why is it called the zero conditional?

Because it comes before the first, second, and third conditionals in the traditional numbering, and unlike them it involves no shift in time or reality: it uses the present simple for both clauses and describes what is simply true. The first conditional moves to a real future (If it rains, I'll stay in), the second to an unreal present (If I had time, I'd stay in), and the third to an unreal past (If I had known, I would have stayed in). The zero conditional is the baseline all three depart from.

English grammar · Intermediate

Zero Conditional Sentences: Form, Uses, and Examples

Written by Eleanor Whitfield, Lead English Curriculum Editor · Reviewed September 2026

A zero conditional sentence describes what always happens when a condition is met. Both halves use the present simple: if or when plus a present simple verb states the condition, and a second present simple clause gives the result (If it rains, the match is cancelled). Because the result is automatic, the zero conditional is the form for scientific facts, general truths, rules, habits, and instructions.

If you heat ice, it melts.

a general truth: present simple in both halves

What it is

The zero conditional is the conditional for things that are always true. The if-clause names a situation and the main clause names the result that follows every time, without exception: If you mix blue and yellow, you get green. Both clauses sit in the present simple because neither is about a particular moment; they describe how the world works, how a machine behaves, or what someone habitually does. English uses this form where other languages might reach for a future or a subjunctive, and the logic is simple: if the result is guaranteed, there is nothing uncertain to mark, so the plainest tense does the job.

If you don't water plants, they die. (a general truth: always, for any plants) When I drink coffee after six, I can't sleep. (a personal habit that repeats)

How to spot it

Look for if or when followed by a present simple verb, with a present simple verb in the other clause too. If you can replace if with whenever or every time and the meaning does not change, the sentence is a zero conditional.

If water reaches 100 degrees, it boils. (scientific fact: whenever this happens, that follows)
When the battery runs out, the screen goes black. (how a device behaves, every time)
If I'm late, my boss gets annoyed. (a habitual result in someone's life)
If the light is red, stop. (an instruction: an imperative in the result clause)

The trap is the word if itself. Learners see if and reach for will, but will belongs to the first conditional, which is about one future occasion. If you press this button, the machine stops is a rule; If you press this button, the machine will stop is a prediction about the next time you press it.

Zero Conditional Sentences Quick Reference

What the zero conditional is used for

Use	Example	Why the present simple fits
Scientific facts	If you freeze water, it expands.	true at every time, not a single event
General truths about life	If people feel respected, they work harder.	a pattern, not a prediction
Habits and routines	When I get home, I take the dog out.	what happens every day
Rules and regulations	If a player handles the ball, the referee gives a free kick.	the rule applies every time
How things work	When you click the icon, a menu opens.	the result is built in
Instructions and advice	If the alarm sounds, leave the building.	imperative for the result; the condition is still present simple

Common Zero Conditional Sentences Examples in English

Zero conditionals grouped by what they describe. In each one, swap if for whenever and the sentence still works:

Facts and Science

If you heat metal, it expands.: physical law
Ice floats if you put it in water.: the result clause can come first; no comma needed
When the sun sets, the temperature drops.: when for something that happens regularly
If you don't eat, you get hungry.: negative condition with don't

Facts are the purest zero conditional: there is no imaginable situation where the result fails.

Habits and Routines

If I have time in the morning, I go for a run.: a personal routine
When she's stressed, she cleans the whole flat.: a habitual reaction
My dad always shouts at the TV if his team loses.: always fits naturally in a zero conditional
If we go to that café, we usually sit by the window.: usually shows the habit

Frequency adverbs (always, usually, never) slot in easily because the sentence is already about repeated behaviour.

Rules and How Things Work

If you park here without a permit, you get a fine.: a rule that is applied every time
When you enter the wrong PIN three times, the card is blocked.: how a system behaves; passive result
If the tenant pays late, the landlord charges a fee.: a contract term
The door locks automatically when you close it.: when-clause at the end

Rules written in the zero conditional sound firm and impersonal, which is why it is common in signs, contracts, and manuals.

Instructions and Advice

If you feel dizzy, sit down.: imperative in the result clause
If the printer jams, don't pull the paper out.: negative imperative
When you finish, hand your paper to the invigilator.: exam instructions
If you're not sure, ask.: short advice, still zero conditional

The condition stays in the present simple; only the result changes to an imperative.

How the Zero Conditional Works

Two present simple clauses, one connecting word, and a meaning that covers all time rather than one moment.

Present Simple in Both Clauses

The if-clause and the main clause both take the present simple, including the third-person -s: If she calls, he answers. Nothing else marks the sentence as conditional; the tense choice is what tells the listener that this is a general pattern rather than a one-off.

If the temperature drops below zero, the pipes freeze.

drops and freeze: two present simple verbs

Present simple + present simple.

If and When Mean the Same Thing Here

Because the result always follows, it makes no difference whether you say if or when: If I'm tired, I go to bed early and When I'm tired, I go to bed early describe the same habit. Whenever and every time are stronger versions of the same idea. This interchangeability disappears in the first conditional, where if means the event may not happen and when means it will.

If you press the button, the doors open. When you press the button, the doors open.

identical meaning in the zero conditional

If = when = whenever.

Either Clause Can Come First

Put the if-clause first when you want to set the scene, and last when the result is the news. When the if-clause opens the sentence it is followed by a comma; when it closes the sentence, there is no comma.

If it rains, the roof leaks. The roof leaks if it rains.

comma after a fronted if-clause, none when it follows

If-clause first: comma. If-clause last: no comma.

Negatives and Questions Use Do and Does

Both clauses behave like any present simple clause, so negatives take don't or doesn't and questions take do or does. The if-clause itself is rarely a question, but the main clause can be.

If you don't back up your files, what happens when the laptop dies?

don't in the condition, a present simple question as the result

Ordinary present simple rules apply.

It Is About All Time, Not the Future

The zero conditional says nothing about whether the condition will happen; it says what follows if it ever does. That is why will never appears in it. As soon as you are thinking about one specific future occasion, you have moved into the first conditional and will returns to the main clause.

If it snows, the school closes. If it snows tomorrow, the school will close.

a standing rule vs. a prediction about one day

General rule = no will.

Common Mistakes with Zero Conditional Sentences

Incorrect: If you will heat water to 100 degrees, it boils.

Correct: If you heat water to 100 degrees, it boils.

Will never appears in an if-clause, and in a zero conditional it does not appear in the result clause either. The present simple in both halves is what signals a general truth.

Incorrect: When I am tired, I will go to bed early.

Correct: When I am tired, I go to bed early.

This describes a habit, something that happens every time, so the result takes the present simple. With will the sentence becomes a plan for one particular evening, which is a different meaning.

Incorrect: If he don't sleep enough, he feel terrible.

Correct: If he doesn't sleep enough, he feels terrible.

Both clauses are ordinary present simple clauses, so the third-person forms still apply: doesn't in the negative and feels in the affirmative. The if does not switch the agreement rules off.

Incorrect: If you would mix red and blue, you get purple.

Correct: If you mix red and blue, you get purple.

Would belongs to the second conditional, which imagines something unreal. Mixing paint is a real, repeatable action with a fixed result, so the zero conditional with the present simple is the only fit.

Beyond the Basic Pattern

The result clause does not have to be a plain present simple statement, and if is not the only word that can open the condition.

Imperatives and modals in the result clause

When the zero conditional gives instructions or permission, the main clause takes an imperative or a modal such as can, must, or should. The condition stays in the present simple.

If the engine overheats, turn it off and wait.: imperative result: an instruction
If you have a season ticket, you can use any platform.: can: permission that applies every time
When the red light flashes, you must stop.: must: a standing obligation

Can, must, and should describe a general rule here; they do not turn the sentence into a first conditional.

Unless, as long as, and as soon as

Other conjunctions can replace if while the two-present-simple pattern stays the same. Unless means if not; as long as means only if; as soon as and once mark the result as immediate.

Unless you water them, the seedlings die.: unless = if you don't water them
You can borrow the car as long as you fill the tank.: a condition that must be met every time
As soon as the timer beeps, the oven switches off.: immediate, automatic result

Whenever and every time also work and make the habitual meaning explicit: Every time I call, he's busy.

Quick Check: Zero Conditional Sentences

Complete each zero conditional with the present simple form of the verb in brackets, or an imperative where the sentence gives an instruction.

1. If you ___ (heat) butter, it ___ (melt).

Answer: heat, melts

a fact: present simple in both clauses, -s on melts

2. When she ___ (not / sleep) well, she ___ (be) grumpy all day.

Answer: doesn't sleep, is

a habit; doesn't for the negative

3. If the smoke alarm ___ (go) off, ___ (leave) the building immediately.

Answer: goes, leave

instruction: present simple condition, imperative result

4. Plants ___ (die) if they ___ (not / get) enough light.

Answer: die, don't get

result clause first, so no comma

5. ___ (do) you always ___ (take) the train if it ___ (rain)?

Answer: Do, take, rains

a present simple question about a habit

Zero Conditional Sentences FAQs

What is a zero conditional sentence?: It is a sentence that says what always happens when a condition is met, using the present simple in both clauses. The if-clause gives the condition and the main clause gives the automatic result: If you don't charge the phone, the battery dies. It is used for facts, general truths, habits, rules, and instructions rather than for predictions about one occasion.
What is the difference between the zero conditional and the first conditional?: The zero conditional describes a result that follows every time, so both clauses use the present simple: If it rains, the garden floods. The first conditional predicts the result of one real future possibility, so the main clause uses will: If it rains tomorrow, the garden will flood. The if-clause looks the same in both; the tense of the result clause and the meaning differ.
Can I use when instead of if in the zero conditional?: Yes, and the meaning does not change, because the result is guaranteed either way. If I eat too late, I sleep badly and When I eat too late, I sleep badly are the same sentence. Whenever and every time work as well. The two words only separate in the first conditional, where if leaves the event uncertain and when treats it as sure to happen.
Can the zero conditional have an imperative?: Yes, and this is how English gives conditional instructions. The condition stays in the present simple and the result becomes a command: If the alarm goes off, leave the building. If you feel unwell, stop and rest. The negative imperative works the same way: If the oil smokes, don't add the food.
Why is it called the zero conditional?: Because it comes before the first, second, and third conditionals in the traditional numbering, and unlike them it involves no shift in time or reality: it uses the present simple for both clauses and describes what is simply true. The first conditional moves to a real future (If it rains, I'll stay in), the second to an unreal present (If I had time, I'd stay in), and the third to an unreal past (If I had known, I would have stayed in). The zero conditional is the baseline all three depart from.