commutative (adjective) changeable: erratic
Sinonime: ad-lib, concoct, devise, do off the top of your head, do offhand, fake it, improv, invent, make do,
make up, play it by ear, speak off the cuff, throw together
Antonime: certain, changeless,
constant,
fixed,
lasting,
reliable,
stable,
steady,
sure, unchangeable, undeviating