The rare daily word game sweeping the globe. Find what's hidden in plain sight.
SEROTONIN
Definition of SEROTONIN
noun
An indoleamine neurotransmitter, 5-hydroxytryptamine, that is involved in depression, appetite, etc., and is crucial in maintaining a sense of well-being, security, etc.
Wiktionary · CC BY-SA
Where it comes from
From sero- + tone + -in.
Etymology via Wiktionary (CC BY-SA).
Word DNA
How it is built
OUTLIER scores every word on how unusual it is, and that number is not published. Working it out at the board is the game.
SEROTONIN in OUTLIER
Players have found it on 3 boards so far.
It first turned up on Day 145, 12 October 2026. The most recent board was Day 166, 2 November 2026. Nobody has seen it on a board for 3 days.
First ever to find it
on Day 145, 12 October 2026 - before anyone else in Outlier's history. See the Pioneers
Built from these letters
SEROTONIN starts with S and ends with N. Sorted, its letters read EINNOORST - the shape to hunt for when the grid is scrambled. O and N appear more than once.
Same letters, different word
One other word uses exactly these letters. Worth knowing at the board: an anagram fits a grid the same way.
Words that start SEROTO
Its neighbours in the OUTLIER dictionary - shortest first.
Could you have found SEROTONIN?
OUTLIER is a daily word game. One grid, the same grid for everybody, and the words nobody else spots are the ones that pay. This word was on Day 145 - and most players walked straight past it.
Play today's OUTLIER