By heart means memorised so well that you can repeat it word for word. The most common phrases are learn something by heart and know something by heart: poems, phone numbers, song lyrics, lines in a play.
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learn + something + by heart; know + something + by heart; from memory (= without looking)
- As a child, I had to learn a long poem by heart for the school concert.
- I still know my grandmother's old phone number by heart.
- Don't just learn useful phrases by heart; practise using them in your own sentences.
What changed
First versionI know my passport number by memory.
RevisionI know my passport number by heart.
By memory looks logical, but English doesn't use this combination. To say you have memorised something, use by heart, most often with the verbs learn and know.
From memory means without looking at notes or a picture: She drew the map from memory. By heart suggests that a text or number has been learned word for word: I know the poem by heart. In writing, memorise often replaces learn by heart: memorise key dates.
Your turn
We've sung this song at every family party, so I know all the words ___.
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by heart — The song has been sung many times, and the words are remembered exactly: by heart. By memory may sound possible, but English speakers don't say it.
Think of something you know by heart: a poem, a song or a number. Write what it is and why you learned it, using by heart.
I know a short Pushkin poem by heart because we had to learn it at school.
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