One shape laid on top of another, with nothing sticking out anywhere along the edge. Congruent can be thought of as that moment of fitting: two things brought together and no gap, no clash, nothing left over.
Latin congruo meant to meet together, to agree: two sides coming to the same point. The modern word still keeps that meeting point.
拉丁文 congruō 的意思是「一起走到、彼此相合」。可以想成兩邊各自走過來，在同一點碰上。今天的 congruent 還守著這個碰頭的畫面。
Wiktionary entry supplied in this batch's evidence packet (source_ref kaikki:3f6f69a190036ae4:840697552): from Latin congruens, present active participle of congruo (meet together, agree).
Two branches
數學：真的疊得起來
這一家就是核心畫面本身，不用轉彎：東西真的可以重合。
adjective · C1
In geometry, two shapes are congruent when they have exactly the same size and exactly the same shape, so one would lie on top of the other with nothing sticking out. It is said most often about triangles.
全等的
一般與正式用法：兩邊對得上
把疊合的畫面從紙上的圖形，搬到看不見的東西上。
adjective · C1
If one thing is congruent with another, the two fit together well: they agree, they match, or at least they do not clash. It is a formal word, used most often about ideas, plans, values, results, and the way people behave.
相符的、一致的