Extraneous
adjective
not belonging to that in which it is contained; introduced from an outside source
“water free of extraneous matter”
Similar: foreign
adjective
not pertinent to the matter under consideration
“an issue extraneous to the debate”
Similar: immaterial, impertinent, orthogonal
adjective
coming from the outside
“extraneous light in the camera spoiled the photograph”
Similar: external, outside
adjective
not essential
“the ballet struck me as extraneous and somewhat out of keeping with the rest of the play”
Word family
extraneousness