920. I. The principal parts of root verbs and of verbs in #-ere# are
formed in a variety of ways and are best learned separately for every
verb (922-986).
921. II. The principal parts of verbs in #-āre#, #-ēre#, and #-īre#, are
usually formed as follows:
laudō, _praise_ laudāre laudāvī laudātus
moneō, _advise_ monēre monuī monitus
audiō, _hear_ audīre audīvī audītus
For other formations, see 989-1022.