Yes, only is a Scrabble word!

Adverb

1. And nothing more

2. Without any others being included or involved

3. With nevertheless the final result

4. In the final outcome

5. Except that; only this time she came out better"

6. Never except when

7. As recently as

Adjective

1. Being the only one; single and isolated from others

2. Exclusive of anyone or anything else