by heart

• (Received Pronunciation) IPA^(key): /baɪ ˈhɑːt/
• (General American) IPA^(key): /baɪ ˈhɑɹt/

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by heart

1. (idiomatic) From unaided memory and in full detail.

   He used to live in that town, and he still knows all the streets by heart.

   • 1906, The Monthly Musical Record‎, volume 36, page 55:

     You should play over all the pieces you know by heart at least once a month or oftener with the printed copies before you: or all sorts of wrong notes may creep in, and you will be leaving out some crescendo, or rallentando, or sforzato.

   • 1943 November – 1944 February (date written; published 1945 August 17), George Orwell [pseudonym; Eric Arthur Blair], Animal Farm […], London: Secker & Warburg, published May 1962, →OCLC:

     None of the other animals on the farm could get further than the letter A. It was also found that the stupider animals, such as the sheep, hens, and ducks, were unable to learn the Seven Commandments by heart.

Usually used with learn or know.

• off by heart

• by rote (usually pejorative)

• byheart

• “by heart”, in OneLook Dictionary Search.

• breathy