Zero Conditional (Facts and Rules)

Level: A2. The zero conditional is the sentence you use for things that are always true — the result follows the condition every single time. It is the easiest conditional to build because both verbs stay in the present simple.

The rule

A conditional sentence has two parts: an if-clause (the condition) and a main clause (the result). A clause is just a group of words with its own verb.

In the zero conditional, both clauses use the present simple — the base verb, with -s for he, she and it. You use it when the result is always true: a fact, a law of nature, a fixed rule, or an automatic reaction. There is no doubt and no particular time; whenever the condition happens, the result happens too.

• If you heat ice, it melts. (a fact, every time)
• If I am tired, I go to bed early. (my personal rule)

Because the result is certain, you can swap if for when with almost no change in meaning: When you heat ice, it melts. Both say the same thing — the result always follows. That is the clearest sign a sentence is zero conditional and not a prediction about one future moment.

Word order is flexible. You can put the if-clause first or second. When the if-clause comes first, separate the two halves with a comma. When the main clause comes first, you do not need one.

• If you press this button, the machine stops. (comma)
• The machine stops if you press this button. (no comma)

You can also give an instruction in the main clause by using the imperative (the command form): If the light turns red, stop. This is common in rules and directions.

Forms

The pattern never changes: present simple + present simple. The only thing that moves is whether the if-clause or the result comes first.

How to say it

The zero conditional has no special grammar sounds, but two small things trip up learners:

• if is a short, quick word — do not stress it. The stress falls on the content words: If you HEAT ice, it MELTS.
• Many result verbs take the -s ending for it, pronounced three ways: melts ends in /ts/, boils ends in /z/, and freezes and rises add the extra syllable /ɪz/. Match the ending to the sound before it.

A tiny pause at the comma (when the if-clause is first) helps the listener hear the two halves.

Example sentences

1. If you heat ice, it melts.
   A physical fact — always true.
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2. If you mix blue and yellow, you get green.
   An automatic result.
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3. When the sun goes down, it gets dark.
   'When' = 'if' for things always true.
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4. Water boils if you heat it to 100 degrees.
   Main clause first — no comma.
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5. If I drink coffee at night, I do not sleep well.
   A personal always-true result.
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6. Plants die if they do not get water.
   A general truth about plants.
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7. If you press this button, the door opens.
   A machine rule.
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8. When you freeze water, it turns to ice.
   'When' with a scientific fact.
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9. If my phone battery is low, it shows a red light.
   An automatic signal.
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10. Ice floats if you put it in water.
    A fact, main clause first.
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11. If the light turns red, stop.
    Imperative in the result — a rule.
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12. When it rains, the streets get wet.
    A reliable everyday result.
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13. If you do not water the garden, the plants dry out.
    Negative condition, present simple.
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14. Metal expands when it gets hot.
    Scientific law, 'when' + result.
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15. If you touch fire, you burn your hand.
    A painful but general truth.
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16. The alarm sounds if someone opens the window.
    A security rule.
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17. If you leave milk in the sun, it goes bad.
    An everyday automatic result.
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18. When babies are hungry, they cry.
    A general fact about babies.
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19. If you add salt to water, the boiling point rises.
    A science fact with -s on 'rises'.
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20. People get hungry if they skip breakfast.
    A general human result.
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Common mistakes

• ❌ If you will heat ice, it melts. → ✅ If you heat ice, it melts. Never use will in the zero conditional — both verbs are present simple.
• ❌ If you heat ice, it will melt. → ✅ If you heat ice, it melts. A result that is always true stays present; will turns it into a one-time prediction (that is the first conditional).
• ❌ If it rains, the streets gets wet. → ✅ If it rains, the streets get wet. The streets is plural, so no -s on the verb.
• ❌ When you will press the button, the door opens. → ✅ When you press the button, the door opens. When also takes the present simple here.
• ❌ If you heat ice it melts. → ✅ If you heat ice, it melts. Use a comma when the if-clause comes first.

A short conversation

A: Why does the kitchen light keep turning on by itself? B: It is not by itself. If you walk past the sensor, the light comes on. A: Oh, so when I move, it switches on automatically? B: Exactly. And when nobody moves for a minute, it switches off again.

Usage notes

• If vs when. In the zero conditional they overlap because the result is certain. Prefer when for things that definitely happen (When it rains, I take an umbrella) and if for conditions you want to sound more neutral (If it rains, the match stops). Both are correct.
• Rules and instructions. Manuals, recipes and signs love the zero conditional, often with an imperative result: If the engine overheats, turn it off.
• No specific time. The zero conditional is timeless. If you are talking about one particular future moment — if it rains tomorrow — you usually need the first conditional with will, not the zero conditional.

Compared with…

• First conditional. The zero conditional is about things that are always true; the first conditional is about one likely future situation and its result. Compare If you heat ice, it melts (a fact) with If you heat this ice, it will melt (a prediction about this ice, now). The giveaway: zero uses present + present, first uses present + will.
• Second conditional. The second conditional is about unreal or imaginary situations and uses the past tense with would: If I had wings, I would fly. The zero conditional, by contrast, only describes what is real and always true.

To build the zero conditional confidently, make sure you are solid on the present simple first.

Quick recap before you practise.

Practice

Practice

Zero conditional practice

Try each one, then press Check. No sign-up, nothing is sent anywhere — it all runs in your browser.

1 Choose the correct form: 'If you heat ice, it ___.'

will melt melts melted is melting

Check

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melts — The zero conditional uses present simple in both clauses: melts.

2 Complete with the present simple of 'get': When it rains, the streets ____ wet.

Check

Hint: plural subject 'the streets'

Show answer

get — 'The streets' is plural, so no -s: get.

3 Put the words in order to make a correct zero conditional.

itmeltsyouiceIfheat

CheckReset

Show answer

If you heat ice it melts — If-clause (present) + result (present): If you heat ice, it melts.

4 Match each condition to its always-true result.

• If you heat water, Match for If you heat water, — choose — it becomes ice.it boils.it falls.they die.
• If you freeze water, Match for If you freeze water, — choose — it becomes ice.it boils.it falls.they die.
• If you drop a ball, Match for If you drop a ball, — choose — it becomes ice.it boils.it falls.they die.
• If plants get no water, Match for If plants get no water, — choose — it becomes ice.it boils.it falls.they die.

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• If you heat water, → it boils.
• If you freeze water, → it becomes ice.
• If you drop a ball, → it falls.
• If plants get no water, → they die.

Every pair is a general fact, so both verbs stay present simple.

5 Which sentence is a zero conditional?

If it rains tomorrow, we will stay home. If you mix red and white, you get pink. If I had money, I would travel. If you heat ice, it will melt.

Check

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If you mix red and white, you get pink. — Present + present for an always-true fact. The others use will or would.

Quiz

Check yourself

Zero conditional quiz

12 questions · pick an answer and you'll see straight away if it's right.

0/12 0 answered

1. 1The zero conditional is used for…

   A imaginary situations B things that are always true C polite requests D the distant past
   Show answer

   things that are always true — It describes facts, rules and results that are always true.

2. 2Complete: 'If you ___ plants, they grow.' (water)

   A will water B water C watered D watering
   Show answer

   water — Both clauses take the present simple: water.

3. 3Complete: 'Ice ___ if you leave it in the sun.' (melt)

   A melts B will melt C melted D melt
   Show answer

   melts — 'Ice' = it, so present simple + -s: melts.

4. 4Which word can usually replace 'if' in a zero conditional?

   A would B when C will D did
   Show answer

   when — Because the result always happens, 'when' works the same as 'if'.

5. 5Choose the correct sentence.

   A If you will press the button, it opens. B If you press the button, it will open tomorrow. C If you press the button, it opens. D If you pressed the button, it opens.
   Show answer

   If you press the button, it opens. — Zero conditional: present simple in both halves.

6. 6Where does the comma go? 'If it rains ___ the streets get wet.'

   A no comma needed B a comma after 'rains' C a comma after 'streets' D a comma after 'if'
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   a comma after 'rains' — When the if-clause comes first, put a comma between the two clauses.

7. 7Complete: 'When metal ___ hot, it expands.' (get)

   A gets B will get C got D getting
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   gets — 'Metal' = it, present simple: gets.

8. 8Which sentence is WRONG?

   A If you touch fire, you burn yourself. B If you heat water, it will boils. C When the sun sets, it gets dark. D Plants die if they get no water.
   Show answer

   If you heat water, it will boils. — 'Will boils' is doubly wrong: zero conditional has no 'will', and 'will' is never followed by -s.

9. 9Complete the instruction: 'If the alarm rings, ___ the building.'

   A you will leave B leaving C leave D leaves
   Show answer

   leave — A rule can use the imperative in the result: leave.

10. 10Complete: 'The light ___ on if you move.' (come)

    A comes B will come C came D come
    Show answer

    comes — 'The light' = it, so present simple: comes.

11. 11Type the present simple of 'freeze': When the temperature drops, water ____.
    Check
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    freezes — 'Water' = it, so add -s: freezes.

12. 12What is the difference between zero and first conditional?

    A Zero is past, first is present B Zero is a fact (present + present); first is a likely future (present + will) C They mean the same thing D Zero uses 'would'
    Show answer

    Zero is a fact (present + present); first is a likely future (present + will) — Zero = always-true fact; first = one likely future result with 'will'.

Recap cheat-sheet

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