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 meter延伸仪extension speed伸长速率extension shaft套管伸缩轴extension curve延展曲线extension clamp牵引夹extension tongs伸缩钳extension event伸展性项目extension piece内外螺纹管接头extension scale延长刻度,扩展刻度extension shank加长杆