Yhteisvaikutuksessaan

Yhteisvaikutuksessaan is a Finnish grammatical form based on the noun yhteisvaikutus, meaning a joint or interaction effect. The word in inessive form indicates “in its joint effect” or “in its interaction,” with an additional third-person possessive suffix to specify ownership. It is used to refer to the combined effect produced by two or more factors, substances, or processes, as opposed to the effect of any single factor alone.

In practice, the term appears in fields such as pharmacology, toxicology, chemistry, and statistics. In pharmacology and toxicology, yhteisvaikutuksessaan describes how two or more substances interact to modify overall efficacy, safety, or toxicity. In statistics and research, the concept relates to interaction effects where the influence of one variable depends on the level of another variable. The plural form yhteisvaikutukset refers to interactions in general, while yhteisvaikutuksessaan is used when discussing the interaction as it pertains to a specific subject or instance.

Morphology and usage notes: the form combines yhteisvaikutus (joint or interaction effect) with the inessive suffix -ssa/-ssä and the third-person possessive suffix -nsa/-nsä, yielding -yhteisvaikutuksessaan. This construction is typical in Finnish for expressing location or state (“in”) together with possession.

Example: Esimerkiksi kahden lääkeaineen yhteisvaikutuksessaan voidaan havaita synerginen vaikutus, jolloin kokonaisvaikutus on suurempi kuin aineiden erikseen. This illustrates how the phrase functions to describe a combined effect that differs from individual effects.