Yes, sin is a Scrabble word!
...and is worth 3 points in Scrabble, and 4 points in Words with Friends
sin
Verb
1. Commit a sin; violate a law of God or a moral law
2. Commit a faux pas or a fault or make a serious mistake
Noun
1. Estrangement from god
2. An act that is regarded by theologians as a transgression of God's will
3. Ratio of the length of the side opposite the given angle to the length of the hypotenuse of a right-angled triangle
4. (Akkadian) god of the Moon; counterpart of Sumerian Nanna
5. The 21st letter of the Hebrew alphabet
6. Violent and excited activity
What Scrabble words can I make with the letters in sin?
3 Letter Words
2 Letter Words