Zero Conditional

The zero conditional (also called conditional type 0 or if clauses type 0) is used to talk about things that are always true — scientific facts, natural laws, general truths, and habitual actions. It is the simplest of all conditional sentences in English and the foundation for understanding all other conditional types.

There are 3 things to master with the zero conditional: 1 formula (If + present simple, present simple), 3 connectors (if, when, unless), and 4 contexts where you use it (scientific facts, general truths, habits, and instructions). By the end of this lesson, you'll be confident using all of them.

Prerequisite: The zero conditional is built entirely on the present simple tense. If you're not comfortable forming present simple sentences (including third person -s and don't/doesn't), review that lesson first.

The Basic Formula: If + Present Simple, Present Simple

The zero conditional has one simple rule: both clauses use the present simple tense.

This structure tells us: every time the condition happens, the result always happens. It's not about a specific situation — it's about a general truth. You'll also see this pattern called an "if clause" structure, because the condition starts with "if".

Scientific Facts and Natural Laws

• If you heat water to 100°C, it boils.
• If ice gets warm, it melts.
• Metal expands if you heat it.
• Wood floats if you put it in water.
• If you add salt to water, the boiling point rises.

General Truths and Typical Behaviour

• If a baby is hungry, it cries.
• Plants die if they don't get enough water.
• If people don't get enough sleep, they feel tired.
• If a dog is happy, it wags its tail.

Clause Order: If-clause First or Second

You can put the if-clause first or second — the meaning stays the same. The only difference is punctuation:

Tip: When the if-clause comes first, it sets the scene — the reader expects a result to follow. When the result comes first, the sentence feels more direct.

👉 Practice Zero Conditional Basics: Facts & General Truths →

Negative Forms, "When", and "Unless"

Once you know the basic formula, the next step is expanding it with negatives, alternative connectors, and imperatives.

Negative Forms: Don't and Doesn't

Use don't or doesn't to make either clause negative — just like in any present simple sentence.

Both clauses can be negative at the same time:

• Children don't learn well if they don't sleep enough.

"When" = "If" in Zero Conditional

In the zero conditional, "when" and "if" are interchangeable because the result always happens. There is no uncertainty.

Note: This interchangeability only works in zero conditional. In first conditional, "if" and "when" have different meanings: "If it rains tomorrow" (maybe it will) vs "When it rains tomorrow" (I'm sure it will).

"Unless" = "If ... Not"

Unless is a shortcut for "if ... not". It already contains the negative, so never add another negative after it.

⚠️ Common Trap — Double Negative with "Unless":

• ❌ Unless you don't wear sun cream, you get sunburnt.
• ✅ Unless you wear sun cream, you get sunburnt.

Because "unless" already means "if not", adding "don't" creates a double negative and reverses the meaning.

Imperatives in the Result Clause

The zero conditional can pair an if-clause with an imperative (a command or instruction) instead of a present simple statement. This is very common in rules, instructions, and safety notices.

• If it rains, take an umbrella.
• If you feel dizzy, sit down immediately.
• If you see a red warning light, turn the engine off.
• If there is a fire, leave the building calmly.

👉 Practice Negatives, "When" & "Unless" →

Real-life Zero Conditional: Habits, Instructions, and Science

The zero conditional appears everywhere in daily life. Here are the most common real-world contexts.

Daily Habits and Routines

Use the zero conditional to describe what always happens in your life or someone else's life.

• When my alarm goes off in the morning, I get up immediately.
• My boss gets angry if employees arrive late.
• If the traffic is bad, I take the train instead.
• My children watch television when they get home from school.

Instructions and Rules

The zero conditional is the natural way to give general instructions, safety rules, and how-to guidance.

• If you press the 'off' button, the screen goes dark.
• The washing machine doesn't start unless you close the door firmly.
• The car doesn't work unless you turn the key.
• If you hear the fire alarm, use the nearest exit.

Science and Nature

Scientific explanations frequently use the zero conditional to state cause and effect relationships that are always true.

• If you leave metal in salt water, it rusts faster.
• When iron gets wet, it starts to rust.
• When you add baking soda to vinegar, it fizzes.
• Sound travels faster when it passes through water.
• If there are no clouds at night, the temperature drops sharply.

👉 Practice Real-life Contexts: Habits, Instructions & Science →

Zero Conditional vs First Conditional

Understanding the difference between the zero and first conditional is the most important distinction for learners at A2–B1 level. These two conditional types look similar, but they describe fundamentally different situations.

The Key Decision: Always True or Specific Future?

The "Will" Trap

🚨 This is the #1 mistake learners make with the zero conditional.

When you see a cause-and-effect sentence, your instinct may be to use "will" in the result clause — because it feels like a prediction. But in the zero conditional, there is no prediction. The result is a fact, not a future possibility.

Ask yourself: Is this always true, or am I talking about a specific situation?

• Always true → zero conditional (present simple in both clauses)
• Specific future possibility → first conditional (will + base verb in result clause)

Side-by-Side Comparison

Notice the pattern: Zero conditional sentences have no specific time reference — they are general statements. First conditional sentences often include time markers like "tomorrow", "tonight", "this weekend", or "this semester".

Context Clues: Which Conditional to Choose?

👉 Practice Zero vs First Conditional →

Common Mistakes to Avoid

Quick Summary

The Formula:

If + present simple, present simple — for things that are always true.

Connector Equivalences:

Decision Guide: Zero or First?

4 Common Contexts:

1. 🔬 Scientific facts — If you mix oil and water, they separate.
2. 🌍 General truths — If people don't eat, they die.
3. 🔄 Habits — When I get home, I make a cup of tea.
4. 📋 Instructions — If there is a fire, leave the building calmly.

Practice Tips

1. Start with science: Think of 5 scientific facts and write them as zero conditional sentences. This builds the "always true → present simple" connection.
2. Describe your daily routine as zero conditional: "When my alarm goes off, I get up. If I don't eat breakfast, I feel tired." This makes the pattern automatic.
3. Test yourself with "will": Every time you want to use "will" in a conditional sentence, ask: "Is this always true, or just about a specific situation?" If it's always true, remove "will".
4. Practice "unless" conversion: Take an "if...not" sentence and rewrite it with "unless". Then check: did you accidentally keep the negative?
5. Read instruction manuals: Real-world instructions (appliances, safety signs, recipes) are full of zero conditional sentences — notice how they use "if" + imperative.

Practice All Exercises

Ready to practise? These zero conditional exercises online come with answers and explanations for every question. Work through all 4 sets, from basic if clauses exercises to the zero and first conditional challenge:

Now try the exercises to practice what you've learned!