By suppression of the second alternative, whether comes to introduce a simple indirect question, and becomes the ordinary sign of indirect…
Introducing an indirect question: if, whether. Obsolete (nonstandard or regional).
英语词典包含1132095条英英释义在线翻译词条，基本涵盖了全部常用单词的英英翻译及用法，是英语学习的有利工具。