The verbal stem –essō (rarely -issō) may be grafted onto existing verbs to denote a certain energy or eagerness of action (though not necessarily repetition.)
- Capiō (take) —> capessō (snatch)
- Faciō (do) —> facessō (do eagerly)
- Petō (seek) —> petissō (look frantically for)
Declension of such verbs is usually third declension for present and infinitive, but fourth declension for perfect and supine.
- Capessō, capessere, capessīvī, capessītum
- Petissō, petissere, petissīvī, petissītum
This is somehow related to the rare variant of the future perfect stem -āssō.
- amāssis (for ameris)
- although these forms are so rare that there’s no complete declension of any one verb in this form in all extant Latin literature, fragmentary appearances suggest that these too would follow the third (present, infinitive) / fourth (perfect, supine) pattern
The Essential AG: 183.5, 263.2b, 236.2bn