a special skill or ability that you have naturally or can learn 技能；本领
It’s easy, once you’ve got the knack.
你一旦掌握这个技能就容易了。
~ of/for (doing) sth
He’s got a real knack for making money.
他有赚钱的真本领。
~ of doing sth a habit of doing sth 习惯；癖好
She has the unfortunate knack of always saying the wrong thing.
不幸的是，她总是说错话。