Collins COBUILD Advanced Learner's English Dictionary - whether

Frequency: The word is one of the 700 most common words in English. 1. You use whether when you are talking about a choice or doubt between two or more alternatives. To this day, it’s unclear whether he shot himself or was murdered... They now have two weeks to decide whether or not to buy... I don’t know whether they’ve found anybody yet. CONJ 2. You use whether to say that something is true in any of the circumstances that you mention. Whether they say it aloud or not, most men expect their wives to be faithful. ...beers and lagers of all kinds, whether bottled or draught. CONJ