adjectives
not pertinent to the matter under consideration
"an issue extraneous to the debate"; "the price was immaterial"; "mentioned several impertinent facts before finally coming to the point"
not essential
"the ballet struck me as extraneous and somewhat out of keeping with the rest of the play"
is similar to
not forming an essential part of a thing or arising or originating from the outside
"extrinsic evidence"; "an extrinsic feature of the new building"; "that style is something extrinsic to the subject"; "looking for extrinsic aid"
not belonging to that in which it is contained; introduced from an outside source
"water free of extraneous matter"; "foreign particles in milk"
coming from the outside
"extraneous light in the camera spoiled the photograph"; "relying upon an extraneous income"; "disdaining outside pressure groups"