While "mention not" is a colloquial expression used in some regions, it is not considered standard English or widely used in formal settings. The phrase is an informal way to respond to someone who has thanked you, and it means that there is no need for them to mention or thank you for whatever you did.
In more formal or professional settings, it is better to use more conventional responses to express acknowledgment and politeness. Some common responses to "thank you" include:
- "You're welcome."
- "Not a problem."
- "No problem."
- "My pleasure."
- "It was nothing."
- "You're very welcome."
Using these more standard responses ensures clear communication and is generally considered more appropriate, especially in professional or formal interactions. However, in casual conversations among friends or in relaxed settings, "mention not" can be used if it is commonly understood and accepted within the group.