extensionsn.伸展；扩大；延长部分；电话分机名词extension的复数形式.extensionn.延长；伸展；延期；扩充；观念发展；增强n.电话分机；特别课程n.[计]文件名extension agency图书馆的在外服务点extension hanger尾管悬挂器extension theory可拓理论extension leader主要延长枝extension tripod伸缩三角架extension system延长方式extension clause延期条款extension closed扩张闭extensional fold伸展褶皱extension splint[医] 伸展夹