英 [ɪkˈstenʃ(ə)n] 美 [ɪkˈstenʃ(ə)n]
n. 延伸，扩展；展期，延长期；扩建部分，延伸部分；（电话）分机；扩展名；（为非全日制学生开设的）进修部；牵伸（术）；外延；广延（性）
[ 复数 extensions ][1]
柯林斯英汉双解大词典
extension /ɪkˈstɛnʃən/ CET4 TEM4
1.N-COUNT An extension is a new room or building that is added to an existing building or group of buildings. (已有建筑或建筑群的) 延伸建筑
2.N-COUNT An extension is a new section of a road or railway that is added to an existing road or railway. (已有公路、铁路的) 延长路段
3.N-COUNT An extension is an extra period of time for which something lasts or is valid, usually as a result of official permission. 延长的期限
4.N-COUNT Something that is an extension of something else is a development of it that includes or affects more people, things, or activities. 延展
5.N-COUNT An extension is a telephone line that is connected to the switchboard of a company or institution, and that has its own number. The written abbreviation is also used. (电话的) 分机 [also N num]
6.N-COUNT An extension is a part connected to a piece of equipment in order to make it reach something further away. (设备的) 延伸部分[1]