Yes, nos is a Scrabble word!
...and is worth 3 points in Scrabble, and 4 points in Words with Friends
nos
Noun
1. A negative
2. A radioactive transuranic element synthesized by bombarding curium with carbon ions; 7 isotopes are known
What Scrabble words can I make with the letters in nos?
3 Letter Words
2 Letter Words