Risking starting a flame-war but I really don't want to, this is a question of curiosity, not looking down/up on any languages: Isn't Scheme "a lisp" even thou

Risking starting a flame-war but I really don't want to, this is a question of curiosity, not looking down/up on any languages: Isn't Scheme "a lisp" even though most people usually distinct them? The similarities between Scheme and Common Lisp seems to be greater than any of the two and Clojure, and usually people refer to Clojure as a Lisp but it's hearsay to claim Scheme is a Lisp. Of course, C2 already have a page on the subject (https://wiki.c2.com/?IsSchemeLisp https://wiki.c2.com/?IsSchemeLisp) so if you want to share a new opinion on the subject, make sure it hasn't already been said :)