Yes, mas is a Scrabble word!
...and is worth 5 points in Scrabble, and 6 points in Words with Friends
mas
Noun
1. Informal terms for a mother
2. A master's degree in arts and sciences
3. One thousandth of an ampere
4. A state in New England; one of the original 13 colonies
What Scrabble words can I make with the letters in mas?
2 Letter Words