cotton on
US /ˈkɑːt.ən ɑːn/
UK /ˈkɑːt.ən ɑːn/

1.
明白, 領會
to understand something after a period of not understanding it
:
•
It took him a while to cotton on to what I was saying.
他花了一段時間才明白我在說什麼。
•
She finally cottoned on to the joke.
她終於明白了這個笑話。