I. (ˈ)in, ən+ adjective
Etymology: probably from French, from Middle French, from in- in- (I) + variable
: consistent , uniform : showing no deviation : unchanging , unfailing
where many words … are relatively invariable in meaning from one sentence to another — I.A.Richards
after dinner … retired to the library, according to his invariable habit — Valentine Williams
was respected for his invariable courtesy and undoubted integrity — H.W.H.Knott
• in·variableness “+ noun
II. noun
: one that remains constant