This is the 5495th most frequent Japanese word.
えい
"えい" (ei) can mean "ray" (the fish) or "eternity" depending on context.
An exclamation used to encourage spirit or motivation.
えい！がんばって！
Hey! Do your best!
Here, 'えい' is used as a short form of '英語' (English language).
えいで映画を見るのが好きです。
I like watching movies using English.
The word 'えいっと' is used as an interjection to represent resolute action.