-lainen

From Proto-Finnic *-lainen, from a toponymic element -la +‎ -inen. Cognate with Estonian -lane, Veps -laine.

Attested since at least the Bible translation of 1548, which uses it in Mark 7.26 (Grekilainen) and Luke 4.27 (Syrialainen), among other places.

-lainen (front vowel harmony variant -läinen)

1. Combined with a place name, forms the noun for the inhabitant of a place; or an adjective meaning "of or relating to (the place)".

   Viro "Estonia" → virolainen "Estonian" (person and adjective)

   Savo → savolainen "Savonian" (person and adjective)

2. Combined with a name, forms an adjective for a member of an organization or other defined group, a follower of philosophy etc.

   Hegel → hegeliläinen

   kokoomus (a political party) → kokoomuslainen

3. Combined with a common noun, forms nouns for people characterized by this noun.

   eläke (“pension”) → eläkeläinen (“pensioner”)

   vuokra (“rent”) → vuokralainen (“tenant, lessee”)

• Usually appended to the genitive or nominative singular stem.
• Place names already ending in -la often do not duplicate the suffix, and their adjective forms may be formed with simply -inen (e.g. Karjala → karjalainen, not ˣkarjalalainen).

Noun:

Adjective:

From compounds with laji (“kind, sort”) +‎ -inen. The origin as a separate word can still be seen in the imperfect accommodation to vowel harmony.

-lainen

1. Combined with a pronoun, forms an adjective relating to the kind or nature of a person or an object.

   eri → erilainen = different

   eräs → eräänlainen +subst. = kind of a + subst.

   mikä → minkälainen or millainen = what kind of?

   sama → samanlainen = similar, of the same kind

   se → sellainen = such, of that kind

   tämä → tällainen, tälläinen (colloquial) = of this kind

2. Combined with the genitive form of an adjective, forms an adjective indicating a smaller degree of the quality than that described by the original adjective.

   heikonlainen = relatively weak

   oikeanlainen = of a right kind (but not the right one)

   viileänlainen = sort of cool

As this suffix is historically a compound, it is not subject to vowel harmony in the standard language; with the exception of the word yhtäläinen, it always has back vowel harmony. In colloquial use it may have a front vowel variant, if not the speaker has not been explicitly taught to avoid that, which proves the rule moot.

• Anneli, Linnea, alinen