When a
Greek word begins either with a
vowel or a
rho, the first
letter must have a
breathing mark above it. There are two breathing marks, one that looks like
(, and one that looks like
). The
( (
rough breathing) simply indicates that you must
pronounce an
h sound before the
word, the
) (
smooth breathing) indicates that there is no h.
A rho will always have rough breathing, without exception. This is why English words which derive from Greek words which begin with rho are spelled in English beginning with rh.