Lmk is an abbreviation of let me know. The abbreviation is used the same way the spelled-out phrase is used, but you should avoid it in formal communication.

What is LMK text?

IMY is an abbreviation of the phrase “I miss you,” and is most often used in text messages and informal communication. It is a simple (and thoughtful) way of telling another person that you miss them.

How do you respond to LMK?

Here it should be mentioned that the appropriate reply for this acronym is LYK which stands for “let you know.” If someone texts you, “LMK when you want to leave”, an appropriate response would be, “Okay, I'll LYK”.