[, ]the act of making sth longer, larger, more complicated, etc.; the thing that is added to do this 延长；扩大；延伸；延长（或扩大）的事物◆The extension of the subway will take several months. 地下人行道延长工程需要好几个月时间。◆We see the website as an extension of our telephone service. 我们把这个网站看作是电话服务的延伸。◆The bank plans various extensions to its credit facilities. 这家银行计划从各方面扩展信贷服务。
[] an extra period of time allowed for sth 延长期；展期◆He's been granted an extension of the contract for another year. 他的合同获准延期一年。◆a 14-month extension to the loan facility 对这笔贷款延期 14 个月
[] a new part that is added to a building （建筑物的）扩建部分◆They are planning a $60 million extension to the airport terminal. 他们正计划斥资 6000 万元对候机楼进行扩建。
[] ( ext.) one of many telephone lines that are connected to a switchboard in a large building, each with its own number （电话）分机，内线◆What's your extension number? 你的分机号码是多少？◆Can I have extension 1125 please? 请接 1125 号分机。
() [] the set of letters that are placed after a dot at the end of the name of a file and that show what type of file it is （计算机文件的）扩展名◆The file must be saved with a .htm extension. 这个文件必须用 .htm 扩展名来贮存。