RHO

Yes. "RHO" is in the ENABLE word list, accepted by Words With Friends and most open Scrabble apps. It scores 6 points in Scrabble and 5 points in Words With Friends.

In Scrabble, "RHO" is worth 6 points before bonuses. In Words With Friends, it's worth 5 points. Played on a triple-word-score, the Scrabble value becomes 18.

The seventeenth letter of the Modern Greek and Classical alphabets and the nineteenth letter of Old and Ancient.

No, "RHO" has no anagrams in the ENABLE dictionary — it's the only word that can be formed from its exact letters.