明暗 めいあん境界 きょうかい せんではありませんでした
meiankyōkaisendewārimasendeshita

Noun
Desu Copula

The polite, past negative form of 明暗境界線

1. It was not the boundary between light and darkness.; It wasn't the light-dark boundary.

Past/Perfective
Negative
Polite
Formal Register
Astronomy