Sisäisen

Sisäinen is a Finnish adjective meaning internal or inner, used to describe things that pertain to the inside, to inner aspects, or to domestic/internal matters within a system. It is formed from the root sisä- meaning inside, joined by the common adjective suffix -inen.

In Finnish, adjectives agree with the noun they modify in number and case. The form sisäisen is the genitive singular of sisäinen, used when the noun it describes is in genitive. Other common forms include sisäinen (nominative singular), sisäistä (partitive singular), sisäisessä (inessive singular), sisäiset (nominative plural), and sisäisten (genitive plural). For example, you can say sisäinen maailma (the inner world), sisäisen maailman tutkimus (the study of the inner world), or sisäisten ovien suunnittelu (the design of the inner doors).

Common usage spans psychology, philosophy, and everyday language. It appears in phrases like sisäinen logiikka (internal logic), sisäinen tila (internal state or condition), and sisäiset asiat (internal matters). The term often contrasts with ulkoinen, meaning external or outer, to distinguish what is internal from what lies outside.

Etymology traces sisäinen to sisä- (inside) plus the adjective suffix -inen, a productive construction in Finnish for forming descriptive adjectives. The word is widely used across formal and informal registers and can modify a wide range of nouns, from abstract concepts to concrete objects.

See also: ulkoinen, sisätilat, sisä- as a prefix, Finnish adjective declension.