Letter between xi and pi (7)

I believe the answer is:

omicron

(Other definitions for omicron that I've seen before include "letter from 13 [HELLENE]" , "character in Europe" , "character in Sophocles" , "old letter" , "Moronic (anag) - Greek letter" .)

I've seen this clue in the Sydney Morning Herald and The Wall Street Journal.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.