1. The Forms of the verb may be referred to four basic Stems, called (1) the Present, (2) the Imperfect, (3) the Perfect and (4) the Future.
NOTE. There are some forms characteristic of each stem, like the suffix -n or -ske/o, which give generally Present stems. But others give different stems depending on their opposition to other forms.
2. There are remains of monothematic verbs, like in the IE II; as in es, to be. And there are also some traces of recent or even nonexistent mood oppositions. To obtain this opposition there are not only reduplications, lengthenings and alternations, but also vowel changes and accent shifts.
3. There are also some other verbs, not derived from root words, the Denominatives and Deverbatives. The first are derived from nouns; as stroweio, strew, sprinkle, from strou, structure; the last are derived from verbs, as, wedeio, inform, from weid, know, guard, look after.
NOTE. It is not clear wether these Deverbatives (causatives, desideratives, intensives, iteratives, etc) are actually derived or are old independent verbs added to other verbs, the one regarded as basic.
5. Reduplication is another forming resort; it consists of the repetition of the root, complete or abbreviated; as in quqlos, wheel.
6. The Stem Vowel has no meaning in itself, but it helps to form different stems, wether thematic or semithematic (those which can be thematic and athematic), opposed to the thematic ones. Thus, It can be used to oppose indicative athematic to subjunctive thematic, present thematic to imperfect athematic, active to middle voice, etc. Sometimes an accent shift helps to create a distinctive meaning.
7. Stems are inflected, as in the declension of nouns, with the help of lengthenings and desinences.