Yes, pen is a Scrabble word!
...and is worth 5 points in Scrabble, and 7 points in Words with Friends
pen
Verb
1. Produce a literary work
Noun
1. A writing implement with a point from which ink flows
2. An enclosure for confining livestock
3. A portable enclosure in which babies may be left to play
4. A correctional institution for those convicted of major crimes
5. Female swan
What Scrabble words can I make with the letters in pen?
2 Letter Words