Meaning of the word "by definition" in English

What does "by definition" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

by definition

US /baɪ ˌdɛf.ɪˈnɪʃ.ən/
UK /baɪ ˌdɛf.ɪˈnɪʃ.ən/

Phrase

as a matter of course; by its very nature

Example:
A square, by definition, has four equal sides.
He's a bachelor, so by definition, he's unmarried.