$Version
is a string that gives the version of the Wolfram Language kernel you are running.
Examples
Basic Examples (1)
Wolfram Research (1988), $Version, Wolfram Language function, https://reference.wolfram.com/language/ref/$Version.html.
Text
Wolfram Research (1988), $Version, Wolfram Language function, https://reference.wolfram.com/language/ref/$Version.html.
CMS
Wolfram Language. 1988. "$Version." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/$Version.html.
APA
Wolfram Language. (1988). $Version. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/$Version.html