conditionals 1

provided/providing (that), so/as long as, only if, on the condition that

to emphasise that the condition is necessary to the result

only refer to present or future conditions; we do not use them with the third conditional

whether ... or not

to express alternative conditions

They'll deliver the furniture whether there's someone to receive it or not.

unless for a negative condition

​we often unless to express a negative condition - means 'except if' and is similar to if... not and only if

I wouldn't go there unless I had to.
Unless you've got a doctor's note to say you've passed the medical, they won't allow you to go on the activity holiday.