upsilon

• n. 希腊语的第20个字母

来自希腊语u psilon, 即仅u音，比较epsilon.

upsilon (n.)

20th letter of the Greek alphabet, 1640s, from Greek u psilon, literally "a mere (or bare) 'u;' " so called in later Greek in reference to its sound. The exact reason is variously explained, but it seems to have had something to do with distinguishing it from diphthongs.