(用以引導出兩種非此即彼的可能性)是...或不...Whether or not it rains/, we're playing football on Saturday. 無論下不下雨, 我們星期六一定踢足球。Tell me whether or not you're interested. 告訴我你有沒有興趣。
是不是...; 是否...; 要不要, 是...或不...She has two more weeks to decide whether to sell the house or not. 她有兩星期可以決定要不要買房子。Whether it rains tomorrow or not, we will go hiking. 無論明天是否下雨, 我們將去健行。