Proto-Indo-European verbs
Proto-Indo-European verbs reflect a complex system of morphology, more complicated than the substantive, with verbs categorized according to their aspect, using multiple grammatical moods and voices, and being conjugated according to person, number and tense. In addition to finite forms thus formed, non-finite forms such as participles are also extensively used.
Source: Wikipedia — Proto-Indo-European verbs (CC BY-SA 4.0)