Salvete omnes discipuli clarissimi,
In class we discussed the part of a verb that included the more (or less) then the regular stem and ending. It turns out that linguists have a better term than “that part” (ista pars).
I give you: themes and distinguishers
Themes are the parts of a word that are invariable in all its morphemes.
Distinguishers are the parts of a word that change to indicate its morphology.
So, for example:
We might say that the present “stem” of ago agere ēgī actum is… age-
But we only very rarely see that stem in the wild (e.g. 2nd s. pres. active imperative: age!) because the short ‘e’ at the end of the stem is euphonized when it comes into contact with personal endings.
Instead, thinking of theme and distinguishers in the present indicative active yields:
| theme | distinguisher |
|---|---|
| ag | ō |
| ag | is |
| ag | it |
| ag | imus |
| ag | itis |
| ag | unt |
Note that Stump (who coined the terms “theme” and “distinguisher”) isn’t talking about morphology of Greek specifically but morphology in general. It’s only me that’s applied that to the morphology of Greek in particular.