The Stem contains the idea of the word without relations; but, except in the first part of a compound (as, arti-fex, artificer), it cannot ordinarily be used without some termination to express them.[1][Another exception is the imperative second person singular in -e (as, rege).]
Thus the stem vóc- denotes voice; with -s added it becomes vóx, a voice or the voice, as the subject or agent of an action; with -is it becomes vócis, and signifies of a voice.
NOTE: The stem is in many forms so united with the termination that a comparison with other forms is necessary to determine it.