-isi-

From Proto-Finnic *-ici- (related to Karelian -si- and Veps -isi-), from Proto-Finno-Ugric *-ńće-j, *-nśe-j; derived from the same ending as in -ita (stem -itse-), and probably also the diminutive ending -ise- (see *-inën) + the same ending as in -ia.

-isi-

1. Marker of conditional mood in verbs.

   ‎voi (“he can”) + ‎-isi- → ‎voisi (“he could”)

   ‎katson (“I watch”) + ‎-isi- → ‎katsoisin (“I would watch”)

Appended to the strong verbal stem; final e or i gets absorbed to i instead of forming a diphthong or long vowel, such as juokse- > juoksisi-, and in the case the stem ends in a diphthong, the initial vowel of such is mostly dropped like in past forms for such verbs, such as (indicative) present syön (“I eat”), past söin (“I ate”), conditional söisin (“I would eat”).

• sii