While

The conjunction while is used with the following meanings.

While = during the time that; for as long as; at the same time as

While there is life there is hope.
The girls danced while the boys sang.
While in London, he learned music.

While = whereas; although

While I admire your courage, I think you ought not to go on this dangerous journey.
While I have no money to spend, you have nothing to spend on.

Only

As a conjunction only has the following meanings: except that; but; were it not that; as

The book would be useful to you, only it is expensive.
She is a pretty girl, only she squints a little.
The day is pleasant, only it is slightly cold.

Without

Without is no longer used as a conjunction meaning unless. In older English it was possible.

We cannot play unless he gives us permission. (NOT We cannot play without he gives us permission.)

Without can be used as a preposition. In this case it is followed by a noun.

We cannot play without his permission.

Except

Except is no longer used as a conjunction. In older English it was possible. In modern English, except is used as a preposition.

Everybody had a prize except me.