(1) Adverbs are formed from adjectives by the addition of sti, perhaps related to the suffix of the elative, sta, e.g. hywä, good, hywästi, well; tietty, known; tietysti, certainly. lti is also found (cf. ablative lta); laajalti, widely, e.g. se on laajalti tunnettu, he is widely known; paksulta, much or thickly; syvältä, deeply.
(2) ten or ti (cf. prolative tse) is added to pronouns. Täten, so; miten, how; siten, so; muuten, otherwise; peräti, entirely.
(3) isin (instructive) is added to nouns. Maisin, by land; takaisin, back.
(4) nne is added to pronouns, and forms adverbs of direction. Sinne, thither; tänne, hither; minne, whither; jonnekunne, to somewhere or other.
(5) tusten, tuksin, ksuttain, kkain, are used to form adverbs expressing a mutual relation. Rinnatusten, side by side; käsityksin, hand in hand; peräksyttäin or peräkkäin, one behind the other.
(6) oin, or sometimes ain (probably from ajoin, aika, time), is added to the adessive case of pronouns to form temporal adverbs. Silloin, then; milloin, when; muinoin, formerly.
C. Various cases of nouns are used as adverbs:—
Nominative—E.g. kohta, soon; kyllä, enough.
Accusative or genitive—kauan, long; paljon, much.