constant steadfast in purpose or devotion or affection; "a man constant in adherence to his ideals"; "a constant lover"; "constant as the northern star"
inconstant likely to change frequently often without apparent or cogent reason; variable; "inconstant affections"; "an inconstant lover"; "swear not by...the inconstant moon"- Shakespeare
invariance the nature of a quantity or property or function that remains unchanged when a given transformation is applied to it; "the invariance of the configuration under translation"
metastability the quality of a physical system that persists in its existing equilibrium when undisturbed (or only slightly disturbed) but able to pass to a more stable equilibrium when sufficiently disturbed
