〜を境に: meaning and usage

How to form it

• noun+を境に（して）/を境として
• verb (ta-form)+の+を境に

How it is used

A (a moment, an event or a place) is the dividing line: after it, or on the other side, things are clearly different. Often with 「がらりと」 or 「急に」. Unlike 「を機に」, there is no idea of seizing a chance.

Examples

1. 父が倒れたのを境に母はめっきり元気が無くなった。

   Ever since Dad collapsed, Mom has noticeably lost her energy.

2. この川を境に、言葉のなまりががらりと変わる。

   Cross this river and the local accent changes completely.

3. 四十を過ぎたのを境に、夜更かしがつらくなった。

   Once I turned forty, staying up late became hard going.