know by heart
v.v. to remember something so well that you can say it perfectly without looking at any notes.
v. to have memorised something perfectly; to possess a complete mental record of a text or sequence.
I know all the song lyrics by heart.
She had performed the monologue so many times that she knew it by heart and no longer needed the script.
In an era of digital convenience, the ability to know long passages of poetry by heart is becoming a rare but deeply respected intellectual discipline.
Typically functions as a transitive verb phrase where the object follows 'know'.
contrast with 'memorize' (the process) versus 'know by heart' (the state of having finished the process); the heart was historically believed to be the seat of memory.
I know it from heartI know it by heartThe correct preposition for this idiom is 'by', not 'from'.
Last updated August 2, 2026