conjunction

1. if it be the case or fact that: used to introduce an indirect question ask whether she will help
2. in case; in either case that: used to introduce alternatives, the second of which is preceded by or or by or whether[whether he drives or (whether he) flies, he'll be on time]: sometimes, the second is merely implied or understood [we don't know whether he'll improve (or not)]
3. either taxation to support the war, whether just or unjust

Etymology: ME < OE hwæther (akin to Ger weder, neither) < IE *kwotero-, which (of two) < base *kwo-, who (> what) + compar. suffix

pronoun