Psilosis
Psilosis (/saɪˈloʊsɪs/) is the sound change in which Greek lost the consonant sound /h/ during antiquity. The term comes from the Greek ψίλωσις psílōsis ("smoothing, thinning out")[1] and is related to the name of the smooth breathing (ψιλή psilḗ), the sign for the absence of initial /h/ in a word. Dialects that have lost /h/ are called psilotic.
The linguistic phenomenon is comparable to that of h-dropping in dialects of Modern English and to the development by which /h/ was lost in late Latin.