formation exists in two types: *(é)-y-eti ~ *(é)-y-onti. Accented root in e-grade. This type was primarily used to form transitive imperfective verbs from intransitive perfective verbs. *(∅)-y-éti ~ *(∅)-y-ónti. Zero-grade root with accent on the thematic vowel. This type formed mostly intransitive imperfective verbs, often deponent (occurring only in middle voice). Examples: *wr̥ǵyéti, *gʷʰédʰyeti, *spéḱyeti. sḱe-suffix *(∅)-sḱ-éti ~ *(∅)-sḱ-ónti. Thematic, with zero-grade root and accent on the thematic vowel. This type formed durative, iterative or perhaps inchoative verbs. Examples: *gʷm̥sḱéti, *pr̥sḱéti. se-suffix *(é)-s-eti ~ *(é)-s-onti. Thematic, with accented e-grade root. Examples: *h₂lékseti. Secondary imperfective eh₁-stative *(∅)-éh₁-ti ~ *(∅)-éh₁-n̥ti. This formed secondary stative verbs from adjectival roots, perhaps also from adjective stems. The verbs thus created were, nonetheless, imperfective verbs. This suffix was thematicised in most descendants with a -ye- extension, thus -éh₁ye- as attested in most daughter languages. It is unclear if the verb ablauted; most indications are that it did not, but there are some hints that the zero-grade did occur in a few places (Latin past participle, Germanic class 3 weak verbs). Some scholars, including the editors of the Lexikon der indogermanischen Verben, believe that the eh₁-stem was originally an aorist stem with 'fientive' meaning ('to become X'), whereas the -ye- extension created the present with 'essive' meaning, 'to be x'. Examples: *h₁rudʰéh₁ti. éye-causative/iterative *(o)-éy-eti ~ *(o)-éy-onti. Thematic, affixed to the o-grade of the root, with accent on the suffix. This formed causative verbs, meaning "to cause to do", or iterative verbs, meaning "to do repeatedly". Most branches, like Germanic, preserve the causative meaning, but some (Greek and Slavic) retain mostly the iterative one. Examples: *sodéyeti, *bʰoréyeti, *h₃roǵéyeti. (h₁)se-desiderative This thematic suffix formed desiderative verbs, meaning "to want to do". Two formations are attested: *(é)-(h₁)s-eti ~ *(é)-(h₁)s-onti. Accented full grade of the root. *(í)-(∅)-(h₁)s-eti ~ *(í)-(∅)-(h₁)s-onti. Reduplicated with i, accent on the reduplicated prefix, zero-grade root. Examples: *wéydseti, *ḱíḱl̥h₁seti. sye-desiderative *(∅)-sy-éti ~ *(∅)-sy-ónti. Similar to above, but with an accented thematic vowel and zero-grade root. Examples: *bʰuHsyéti. ye-denominative *-y-éti ~ *-y-ónti. Affixed to noun and adjective stems for a variety of meanings; accent is on the thematic vowel. The thematic vowel of the nominal stem, if any, is retained as e, as is any possible -eh₂ suffix, thus creating the variants -eyé- and -eh₂yé-, which developed into independent suffixes in many daughter languages. h₂-factitive *-h₂-ti ~ *-h₂-n̥ti. This formed factitive verbs from adjective stems. As above, the thematic