grammar → 是…的
TSUMUGU · TBCL 4 (est.) · 語法
是…的 grammar point · tier 2 · 是…的 focus
Focus: foregrounds one detail (time, place, manner, agent) of a known past event.

字源 FORM what the parts do

是 says it is so; 的 pins it to the fact; the detail you stress sits between them.

故事 STORY a scene to remember it by

是 and 的 close like a picture frame, and whatever sits inside is the one thing on show.
自撰記憶法
框 · Frame
[subj] 是 [focused detail] 的
例 · Examples
1我是昨天到的。
It was yesterday that I arrived.