if/ɪf/
conj.1. 如果；假如If you ask him, he will help you.如果你向他请求，他会帮助你。
If need be, we'll work all night.如果需要，我们就干个通宵。
2. 即使；虽然We'll go even if it rains.即使下雨我们也要去。
3. 是否She asked if that was enough.她问那是否够了。
He asked if Mr Gilbert's operation had been successful and the doctor told him that it had been.他问吉尔伯特先生的手术是否成功，医生告诉他，手术是成功的。