- epsilon (n.)
[epsilon 词源字典]
- from Greek, literally e psilon "bare -e-, -e- and nothing else," so called by late grammarians in contradistinction to the diphthong -ai-, which had come to have the same sound. Greek psilon "smooth, simple" is of uncertain origin (Watkins suggests PIE root *bhes- (1) "to rub").[epsilon etymology, epsilon origin, 英语词源]