Zero & first conditional

A2 28 / 50

In short

A conditional sentence has two parts: an if-clause (the condition) and a result. Use the zero conditional for things that are always true, and the first conditional for real, possible situations in the future.

The rule

A conditional has two clauses. One starts with if (or when); the other is the result.

Zero conditional - facts, general truths, and automatic results (cause -> effect). Both verbs are in the present simple. Here if and when mean almost the same thing (“every time”):

if / when + present simple	,	present simple
If you heat ice,		it melts.
When it rains,		the ground gets wet.

First conditional - one real, possible, or likely situation in the future. Use the present simple after if, and will / can / may (or an imperative) in the result:

if + present simple	,	will / can / may / imperative + base
If it rains,		we’ll stay in.
If you study,		you’ll pass.
If you see her,		tell her.

The crucial rule: do not put will in the if-clause. After if, when, unless, as soon as, before, after, until, use the present simple even though you are talking about the future.

Not: ~~If it will rain, we’ll stay in.~~
Yes: If it rains, we’ll stay in.

unless = if not. Use it for the one situation that stops the result:

I’ll go for a walk unless it rains. (= if it does not rain)

Comma rule: put a comma when the if-clause comes first; use no comma when it comes second.

If you ask him, he’ll help. (comma)
He’ll help if you ask him. (no comma)

Forms & patterns

Type	If-clause (condition)	Result clause	Use
Zero	if / when + present simple	present simple	Always true; automatic result
First	if + present simple	will + base verb	Likely future result
First	if + present simple	can / may + base verb	Possible result / permission
First	if + present simple	imperative (base verb)	Instruction + condition

Useful linking words that also take the present simple (no will):

Word	Meaning	Example
unless	if not	We’ll eat outside unless it rains.
as soon as	immediately when	Call me as soon as you arrive.
as long as / provided (that)	only on this condition	You can stay as long as you stay quiet.
in case	as a precaution	Take a coat in case it gets cold.
until / before / after	time + condition	Wait here until I come back.

Examples

English	Note
If you mix blue and yellow, you get green.	Zero - a general fact; both verbs present simple.
When I drink coffee at night, I can’t sleep.	Zero - automatic result; when = every time.
If you press this button, the machine stops.	Zero - cause and effect that is always true.
If we leave now, we’ll catch the train.	First - a likely future result; will in the result only.
If you don’t hurry, you may miss the bus.	First - may shows a possible result.
Unless you book early, the tickets sell out.	unless = if you do not book early.
I’ll text you as soon as I land.	Future meaning, but present simple after as soon as.
Take an umbrella in case it rains later.	in case = a precaution; present simple, no will.

Common mistakes

~~If it will rain, we stay home.~~ -> If it rains, we’ll stay home. - No will in the if-clause; will goes in the result.
~~When you will be ready, call me.~~ -> When you’re ready, call me. - Present simple after when for future time.
Unless you don’t study, you’ll fail. -> Unless you study, you’ll fail. - unless already means “if not”; don’t add a second negative.
~~If you heat ice it will melt.~~ -> If you heat ice, it melts. - A general truth is zero conditional (present simple), not will.
If you ask him he’ll help (missing comma) -> If you ask him, he’ll help. - Add a comma when the if-clause comes first.

Tips

Quick test: is it always true (a fact)? Use zero (present + present). Is it one possible future event? Use first (present + will).
The if-clause almost never uses will. Keep will / can / may for the result side only.
Swap unless for “if not” in your head to check it: “unless it rains” = “if it does not rain.”
Order is free: “If…, result” or “result if…”. Just remember the comma only when if comes first.