the penny drops

意味

someone finally understands something after a while

しばらくしてようやく理解する.

例文

1. 1I stared at the maths problem for ages, and then suddenly the penny dropped.
2. 2Sometimes the penny drops only when you try to explain the idea to someone else.
3. 3Leo didn't understand why we were laughing, but after a minute the penny dropped and he laughed too.
4. 4Some pupils need three or four examples of a new rule before the penny drops.
5. 5My sister explained the plot twice, but the penny dropped only when we watched the film again.

文法

節として使う。変化するのは drops だけ（dropped、has dropped）。the penny は単数のまま。