noun Date: circa 1888 a mark ' placed over some initial vowels in Greek to show that they are not aspirated (as in ἐκεî pronounced \\e-ˈkā\\), the absence of aspiration indicated by a mark '
SMOOTH BREATHING
Meaning of SMOOTH BREATHING in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012