(1)是否(if)：He asked me/didn't know～he should make the last attempt. 他问我/不知道是否应该做最后的努力。I wondered～to go to work or (to) stay at home. 我不知道是去上班还是待在家里。He wasn't sure/certain～he ought to leave or stay. 他不能肯定他是应该走，还是应该留下。The decision～to see her was mine alone. 是否去看她是我个人的决定。It all depends on～you can offer me the chance. 这完全取决于你是否给我机会。Don't hesitate about～to accept or decline his invitation. 不要对是接受还是拒绝他的邀请而犹豫不决。W～it will do us harm or good remains to be seen. 这事对我们有害还是有益尚待观察。It was uncertain/doubtful～she would recover. 无法肯定/难以预料她是否能康复。The point is～on his merits we ought to recommend him. 关键的问题是我们是否应根据他的优点来推荐他。

(2)不管……还是(no matter if)：We'll take the next offer，～good or bad. 我们将采纳下一个提议，不管是好是坏。W～from bravery or stubbornness，they did not give in. 不管是出于勇敢还是固执，他们毕竟没有屈服。I shall go，～you come with me or stay at home. 不管你跟我去还是留在家里，我都要去。W～you support me or～they oppose me，I shall do it. 不管你支持我还是他们反对我，我都要做的。All substances，～it be gas， liquid or solid， are made up of atoms. 所有物质，不管是气体、液体还是固体，都是由原子组成的。～by accident or design 无论是出于偶然还是有意为之;～by skill or luck 无论是靠能力还是靠运气;～through choice or obedience 无论是出于自愿还是由于顺从;

whether or not 是否： Can you tell me～or not the train has left(～the train has left or not)? 请问火车是否开走了? The police will find it out，～you confess or not. 不管你招认与否，警察都会查个水落石出。

【辨异】whether 与 if 的区别见IF。

【用法】 1)whether 一般用于从句或不定式前，表示选择; 2)whether与if在意思上相同，都用于间接疑问句，提供选择或要求回答yes或no;但在下列情况下if不能取代whether。1)在动词不定式之前，如：The trouble is whether to speak the truth or to tell a lie.(问题是讲实情还是说谎。) 2)在介词或名词之后，如：It depends on whether he tells the truth or not.(完全取决于他是否讲实情。) The question whether we ought to call for a doctor was not answered. (没人回答是否叫大夫的问题。) 3)在whether or not 的短语中，如： The police asked him whether or not he would tell the truth.(警察询问他是否讲实情。)4)在主语从句中，Whether he tells the truth or a lie is all the same to me.(他讲实情还是说谎对我来说都无所谓。) It's his right whether he tells the truth or a lie.(讲实情还是说谎是他的权利。)