The first conditional and similar structures

We use the first conditional for things which are possible but not certain.

The structure is if + present simple, will + infinitive.

'If I see John, I'll (I will) tell him.'

The if clause or the main clause can come first. If the if clause is first then you need to put a comma (,) between the two clauses. If the main clause is first then no comma -

'I'll tell John if I see him.'

Instead of 'will' we can use 'might' for possibility and 'can' for ability -

 'If I see John, I can tell him' (if you want me to)

We can use 'Unless' to say 'if not' - 'I expect your homework if you don't tell me you have a problem'  =

 'I expect your homework unless you tell me you have a problem'

If something is certain you can use 'when' -


'I'll tell John when I see him this evening'

If one thing depends on another then we use 'as long as' -

'As long as you do the washing up, I'll dry the dishes.'