Snake case

Snake case is a way of writing phrases without spaces, where spaces are replaced with underscores _, and the words are typically all lower case. It's often stylized as "snake_case" to remind the reader of its appearance.

Snake casing is often used as a variable naming convention. The following names are in snake case: left_shift, bitwise_invert, matrix_transpose.

Note that snake case never contains upper case letters. Sometimes, constants are written in all-uppercase, such as JavaScript's Number.MAX_SAFE_INTEGER. This is not typically considered as snake case. Instead, it is sometimes called screaming snake case.

Snake case is the most popular convention in Python, Rust, and various other languages.