A condition may be expressed in several different ways.

By using if

If you heat ice, it melts.
If you work hard, you will succeed.
If it rains, the match will be canceled.

Sometimes if is omitted.

Were I you, I wouldn’t do it.

By using unless

Unless you obey my instructions, you will be dismissed. (= If you do not obey my instructions, you will be dismissed.)
Unless you give me the keys of the safe, you shall be shot.

By using an imperative

Take a step further and see what happens.

By using a conjunctional phrase

In case it rains, I shall put on my raincoat.

By using a participle phrase

Supposing he does not come, what will you do?

Notes
The same conditional sentence or idea may be expressed in several different ways.

He will come if you invite him.
He will not come unless you invite him.
He will come provided that you invite him.
In case you invite him, he will come.

Expressing a concession or contrast

A concession or contrast may be expressed in several ways.

By using though and although

Though he is ill, he is cheerful.

By using the conjunction as

Strong as he was, he could not beat his enemy. (= Though he was strong, he could not beat his enemy.)

By using whatever

Whatever may have been his intentions, he received us cordially.

By using all the same

He is poor; all the same he is content with his lot.

By using even if

Even if he is your enemy, you shall not treat him like that.