n. 希腊字母第15字

[ noun ]
the 15th letter of the Greek alphabet
<noun.communication>

Omicron \O*mi"cron\, n. [Written also {omikron}.] [NL., fr. Gr.
[Omicron] [omicron]. See {Micro-}.]
Lit., the little, or short, O, o; the fifteenth letter of the
Greek alphabet.
[Webster 1913 Suppl.]