Yes. SI is a valid word.
SI is valid in the North American word list used for the Scrabble board game and other crossword tile games.
SI 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 SI
Some systems of singing the scale use si for the seventh note, while others use ti; the word list accepts both, along with TE. Reverse it and you have IS.
Settle the next one at the table: score your game free in Tileside →
SI scores 2 points
Before any bonus squares: S 1 + I 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: SI as the first play
Later in the game, put the S on a 3L square and SI is worth 4 before any word bonus.
Hooks: one tile makes a new word
In front of SI (1):
- PSIa unit of pressure
After SI (10):
Place that one tile so it also forms a word in the other direction and both words score.
Longer words from SI
Other forms of SI (1):
- SISform of SI: the syllable naming the seventh (subtonic) note of any musical scale in solmization
Words that start with SI:
- SIALthe granitelike rocks that form the outermost layer of the earth's crust
- SIBB
- SIBSform of SIB: a person's brother or sister
- SICE
- SICKaffected by an impairment of normal physical or mental function
- SICSform of SIC: intentionally so written (used after a printed word or phrase)
- SIDEa place within a region identified relative to a center or reference location
- SIDH
Change one tile
Swap any one letter of SI and these are still words:
Same letters, other words
Memory tip
SI is another name for TI, the seventh note of the scale (TE is a third spelling). Reverse it for IS.
On these lists
Other two-letter words starting with S
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.