Mood

Etymology

A narrowing of the ordinary noun mood (a temporary state of feeling). Used as a standalone reaction to signal relatability, it spread on Twitter and Tumblr in the late 2010s, frequently paired with a picture or clip that captured the feeling.

interjection · /MOOD/
An expression that something is deeply relatable — that it perfectly captures how you feel.
What it names
It compresses a whole "that is exactly me right now" into one word, turning a shared image or sentiment into instant identification. Intensified as "big mood" or "a whole mood," it lets people agree emotionally without elaboration.
Example
A photo of a cat refusing to leave a warm laundry pile — honestly, mood.
Related idea
Adjacent to calling something a vibe, but a mood claims personal identification ("that’s me"), while a vibe describes an atmosphere something gives off.