Yes. OS is a valid word.
OS is valid in the North American word list used for the Scrabble board game and other crossword tile games.
OS is in the NASPA Word List 2023 (NWL2023), the North American list that Tileside uses for challenges and the one used in club and tournament play.
About OS
Anatomy and law borrowed OS from Latin: a bone, or a mouth or opening. Its plurals are unusual, OSSA for bones and ORA for mouths, and they are valid too. In its third sense, an esker (a long ridge of glacial gravel), the plural is OSAR.
Settle the next one at the table: score your game free in Tileside →
OS scores 2 points
Before any bonus squares: O 1 + S 1 = 2. On a double-word square that's 4, on a triple-word 6, and every letter bonus under one of these tiles is applied first.
Example: OS as the first play
Later in the game, put the O on a 3L square and OS is worth 4 before any word bonus.
Hooks: one tile makes a new word
In front of OS (10):
- BOS
- COSratio of the adjacent side to the hypotenuse of a right-angled triangle
- DOSform of DO: engage in
- GOSform of GO: change location
- KOS(in India) a unit of length having different values in different localities
- MOSform of MO: an indefinitely short time
- NOSform of NO: (quantifier) used with either mass nouns or plural count nouns for indicating a complete or almost complete lack or zero quantity of
- POSform of PO: a European river
After OS (1):
Place that one tile so it also forms a word in the other direction and both words score.
Longer words from OS
Change one tile
Swap any one letter of OS and these are still words:
Same letters, other words
Memory tip
OS is a bone, and also a mouth or opening, from Latin. Its plurals are unusual: OSSA for bones and ORA for mouths.
On these lists
Other two-letter words starting with O
Check words at the table, free
Tileside keeps score, checks words like this one during a challenge, tracks the tiles left in the bag and times turns. It runs in your phone's browser with no account and works offline.
Tileside checks words against the North American list, the NASPA Word List 2023. Your group's chosen dictionary always wins. Playing the international (Collins) list? Turn on its 20 extra two-letter words in Setup.
Word list: NASPA Word List 2023, used under license. NASPA Word List 2023 Edition © NASPA 2023. The copy included in this app is licensed for personal use. You may not use it for any commercial purposes.
Works with the Scrabble board game, played at the table. Tileside is an independent product, not affiliated with or endorsed by the makers of Scrabble.