明暗 めいあん境界 きょうかい せんじゃなかったです
meian kyō kaisenjanakattadesu

Noun
Desu Copula

The polite, past negative form of 明暗境界線

1. Wasn't the boundary between light and dark.; Wasn't a line between brightness and darkness.

Past/Perfective
Negative
Polite
Casual Register
Astronomy