Question 1

What does "by heart" mean?

Accepted Answer

From memory, without needing to read or look.

Question 2

How do you use "by heart" in a sentence?

Accepted Answer

She knows all the lyrics by heart.

Question 3

Is "by heart" formal or informal?

Accepted Answer

"by heart" is register-neutral — appropriate in both casual and formal contexts. Often used with verbs like 'learn' or 'know' to describe memorization.