extension同extent均是extend的名词形式:前者既可作不可数名词，表示“伸展，扩充”，也可作可数名词，表示“附加部分，延伸部分”。例如theextensionof foreign trade（外贸的扩展）和anextensionof one's summer holidays（暑假的延长时间）。后者表达的是“事物延伸的广度，程度，范围等”，如through the whole extent of the country（在全国范围内）。
This cord is not long enough! do you have an extension? 这条绳子不够长！你有长一点的吗？
His leg was now capable of full extension. 他的腿现在能够伸展自如了。
He asked for an extension of his visa. 他申请延长签证有效期。
We built an extension to our house. 我们扩建了我家的房屋。
He sees local history as an extension of family history. 他认为当地的历史是每个人家庭历史的发展。
The country decided to have an extension of government control on the market. 该国决定对市场加强政府监管。
用作名词 (n.)
There are telephone extensions in every office. 每间办公室都有电话分机。
用作名词 (n.)
Method will only return one unique file name per file name extension. 方法对每个文件名扩展名只返回一个唯一文件名。
You can optionally filter the list by extension and keyword contained inthe file name, and also choose to include sub-directories. 你可以按照包含在文件名当中的扩展名和关键字有选择地过滤列表，并且还可以选择包括子目录。
