What is the meaning of 7?

The cardinal number seven.

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

July.

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

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

practical orthography for the glottal stop /ʔ/

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