WHETHER, pronoun or substitute. [Latin The sense seems to be what, or which of two, referring either to persons or to sentences.]
1. Which of two.
WHETHER of them twain did the will of his father? Matthew 21:31/
Here whether is a substitute for one of two, and signifies which; which of the two; but in this sense it is obsolete.
2. Which of two alternatives, expressed by a sentence or the clause of a sentence, and followed by or. Resolve whether you will go or not; that is, you will go or not go; resolve which.
[Note. IN the latter use, which is now most common, whether is called an adverb. This is a mistake. It is the same part of speech as in the former example. The only difference is that in the former example it represents or refers to a noun, and in the latter to a sentence or clause.]