[906.] The perfect participle suffix is -to-, nominative -tus, -ta, -tum, which is often changed to -so-, nominative -sus, -sa, -sum ([912]).
[907.] The perfect participle was originally active as well as passive, and some participles have retained the active meaning: as,
adultus, grown up; ēmersus, rising out from; exōsus, perōsus, hating bitterly; placitus, engaging; iūrātus, sworn, coniūrātus, conspiring; prānsus, having lunched, cēnātus, having dined, pōtus, drunk, &c. The perfect participles of deponents are usually active, but sometimes passive: as, meditātus, having studied, or studied. Many verbs are not accompanied by a perfect participle ([811]), particularly verbs in -ēre, with a parallel adjective in -idus ([287]). Intransitive verbs have usually only the neuter. A perfect active participle meminēns is said to have been used twice (Plaut., Laev.).
[908.] The perfect participle is formed in one of two separate ways:
[909.] (1.) From a theme consisting of a root; in this way the participles of most verbs in -ere and -ēre are formed: as,
gestus, carried, aptus, fit, solūtus, loosed ([142]), iūnctus, joined ([831]), sparsus, sprinkled ([170, 3]); doctus, taught.
[910.] In some consonant root participles of verbs in -ere, -āre, or -ēre, which have the suffix -u- in the perfect stem ([873]), the -to- is preceded by a short i: as, genitus, born ([971-976]); domitus, tamed ([993]); monitus, warned ([1003], [1004], [1009]). In old Latin, e occurs: as, MERETA ([41]); e is retained in vegetus, sprightly. One participle has -tuo-: mortuus, dead.
[911.] Some verbs in -āre have participles from consonant roots: as, frictus, rubbed, fricō, fricāre; see [993]. Also some in -īre: as, fartus, stuffed ([170, 3]), farciō, farcīre; fultus, propped, fulciō, fulcīre; see [1011-1015], and [1017], [1019], [1020].
[912.] Roots in -d- and -t- change -to- to -so-, before which the dentals change to s ([159]). After long vowels, nasals, and liquids the double ss is simplified to s: as, fossus, dug, but dīvīsus, divided; vorsus or versus, turned. The suffix -so- is also found with some roots in -l-, -m-, or -r- and a few others: as, pulsus ([159]).