invariable -
not liable to or capable of change; "an invariable temperature"; "an invariable rule"; "his invariable courtesy"
variable (used of a device) designed so that a property (as e.g. light) can be varied; "a variable capacitor"; "variable filters in front of the mercury xenon lights"
consistent (sometimes followed by `with') in agreement or consistent or reliable; "testimony consistent with the known facts"; "I have decided that the course of conduct which I am following is consistent with my sense of responsibility as president in time of war"- FDR
constant steadfast in purpose or devotion or affection; "a man constant in adherence to his ideals"; "a constant lover"; "constant as the northern star"
