What is the meaning of 7?

The cardinal number seven.

A digit in the decimal system of numbering, as well as octal, and hexadecimal.

an indicator that a chord is a dominant or major seventh chord

tone number 7, typically identified with dark entering yin ru (陰入)

Clipping of 720. (720° spin)

Alternative form of 𨳍 (cat).

Alternative form of 𨳍 (cat).

Alternative form of 𨳍 (cat).

The forty-first letter of the Squamish alphabet, written in the Latin script.

Source: wiktionary.org