搭配 learn something by heart 用心学某事 的意思是 记住某事，即 凭记忆背下来。大家也用 learn something off by heart 表示相同的意思。
例句
She had learnt her presentation off by heart; she didnt look at her notes once!
她把这次演讲要说的话都背下来了，她一次也没看筹备的笔记！
I had to learn poems by heart at school; I can still recite them now.
我上学那会儿要背诗，到目前我还能背下来呢。
Actors have to learn all their words by heart, so that they can remember them during a performance.
演员得牢牢记住台词，如此他们才能在表演时记住要怎么说。