2) Usually with a possessive suffix (active only). 3) Usually with a possessive suffix. Not used with intransitive verbs. Distinct from nouns with the -ma suffix and third infinitive forms. 4) Some uses of the verbal noun are called the 'fourth infinitive' by certain sources (more details).
* The third-person singular indicative form virtaviivaistaa does not exhibit final gemination, unlike the first infinitive (the lemma form), even though they are spelled identically.