As long as, provided, providing

We use as long as to express a condition, to say that something will happen only on condition that something else happens.

It expresses that one thing depends on another.

I'll lend you the book as long as you promise to give me it back next week.
This means: If you don't promise to give the book back next week I will not lend you it.

You can go to the party as long as you come back before midnight.
This means: You can go to the party but you must promise to be back before midnight.

As long as has the same meaning as providing or provided.

You can go to the party, providing / provided you come back before midnight.

We're going skiing next week, providing / provided there's enough snow.