Conditional conjunctions

Conditionals can also be introduced by the following conjunctions,
which do not always have precisely the same meaning as if: as long
as, assuming (that), even if, if only, on (the) condition
(that), in case, provided/providing (that), so long as and unless; also
suppose (that) and supposing (that), which normally introduce
questions [10; 124]:

He’ll definitely win, even if (навіть якщо) he falls over.

They'll lend us their flat on (the) condition (that) (за умови, що) we look after it.

Suppose/Supposing (that) (припустимо, що) we miss the train what shall we do?

In case (“у випадку, якщо”) is used to show possible actions in the future:

I’ll cook plenty of potatoes in case they decide to stay for dinner.

In case they are late, we can always stay in the bar.

We’ll take some more warm clothes on holiday in case the weather changes.

In case is also used to show that somebody did something in the past:

They prepared more vegetables in case there were vegetarians among the guests.

Unless (“якщо тільки не”, “якщо… не”, “хіба”, “окрім як”) is equal to if… not:

Unless the government agrees to give extra money, the theatre will have to close.

We’ll be late unless we leave now.

As long as, provided (that), providing (that) mean “якщо”, “хіба”, “поки”, “доки”:

Providing/Provided (that) (or So/As long as) you clear your desk by this evening, you can have tomorrow off.

Provided (that) there is no opposition, we shall hold the meeting here.

What if and Say can be used in the sense of 'Let us suppose ':
What if/Say he gets home before us and can't get in? What will he do?

What if/Say you were to run out of money, what would you do?

We can abbreviate a condition if we begin a new sentence with If so,
In that case, or If not;or if we continue with in which case :
He may be busy, in which case I'll call later
He may be busy. If so, (In that case,) I’ll call later. If not,
can I see him now⁷

Whether or not introduces 'alternative' conditionals [6; 290]:

Whether I feel well or not on Monday, I’m going back to work.
Whether or not I feel well on Monday, I'm going back to work.
You'll have to put up with it, whether you like it or not.