1. 用来回答感谢或类似于感谢的句子，意为：不用谢；不客气；

--- The film was wonderful. Thank you for inviting me. 这电影很精彩，谢谢你邀请了我。

--- Don’t mention it.  I’m glad you enjoyed it. 别客气，你喜欢就好了。

2. 用来回答道歉，意为：没关系

--- I apologize for what I've said. 我说了那些话，我向你道歉。

--- Don't mention it. 不要这么说。

--- I’m sorry to have troulbed you. 对不起麻烦你了。

--- Don’t mention it. 没关系。

3. 表示某事不重要或无需考虑，意为：那就甭提了；那就算了

Ry sensitive about being small, so don't mention it.  他对自己个子矮小神经过敏，可别提这件事。