Etymology

From Proto-Finnic *-icin. Related to Estonian -si and Livonian -ž. Probably originally an instructive plural form of *-inën (-inen), at least in the non-temporal sense.

Suffix

-isin

Forms temporal distributive adverbs.
‎aamu (“morning”) + ‎-isin → ‎aamuisin (“in the mornings”)

‎maanantai (“Monday”) + ‎-isin → ‎maanantaisin (“on Mondays”)

‎kesä (“summer”) + ‎-isin → ‎kesäisin (“in the summers”)
Used to form some adverbs.
‎väki + ‎-isin → ‎väkisin

Usage notes

-isin adverbs are generally considered to be derived from plural stems, but it is likely that the -i- was always part of the suffix, as with -itse.

Derived terms

See also

Anagrams

-siin, Sini, sini

Finnish