Stem with only one element

Observation
ᐊᐴ Click here to hear this word apuu s/he sits

The stem of a verb like ᐊᐴ apuu s/he sits cannot be broken down into smaller units in which we could identify another stem. Such a stem is called a primary (simple) verb stem with only one element.

In this example, the stem is apu, followed by the third person ending (or inflection) -u.