矣 yǐ particle of completed action

源How it came to be

An arrow with a curl over it, the shaft already gone and the bowstring still moving. That is exactly what it marks in a sentence: the thing has happened and cannot be called back.

用How it is used

• A classical sentence-final particle marking completed action or exclamation - roughly 'now/already/indeed' - 悔之晚矣 (huǐzhī-wǎnyǐ) too late for regrets now, 大势去矣 (dàshì qù yǐ) the game is up.
• Purely Classical Chinese; recognize it in idioms, don't use it in modern writing.

字Characters built with 矣

• 唉 alas
• 挨 next to