Crossword Clue:

Letter between sigma and upsilon

AnswerCrossword Clue
TAULetter between sigma and upsilon
TAUBetween sigma and upsilon.
PHILetter between upsilon and chi
RHOLetter between pi and sigma
TAUSigma-upsilon go-between
SIGMAIt's halfway between pi and upsilon
PHIIt is between upsilon and chi.