the penny drops

US /ðə ˈpɛni drɑps/
UK /ðə ˈpɛni drɑps/
"the penny drops" picture
1.

akhirnya mengerti, paham

used to say that someone has finally understood something, especially after a period of not understanding

:
It took him a while, but then the penny dropped and he realized his mistake.
Butuh waktu baginya, tapi kemudian dia akhirnya mengerti dan menyadari kesalahannya.
I kept explaining, but it wasn't until I drew a diagram that the penny dropped.
Saya terus menjelaskan, tetapi baru setelah saya menggambar diagram, dia akhirnya mengerti.