perustellisesti

Perustellisesti is a Finnish adverb meaning “in a justified, well-grounded, or reasoned manner.” It is derived from the verb perustella (to justify, to base on, to establish) with the adverbial suffix -sti, and is related to the noun perusta (basis, foundation). The word signals that a claim, argument, or decision is supported by reasons, evidence, or logical connections rather than by assertion alone.

Usage in Finnish is predominantly formal and written, such as in academic, legal, or analytical contexts. It indicates that a statement is justified by facts, data, or coherent reasoning. In everyday speech, speakers may opt for simpler phrasing, but in formal texts perustellisesti strengthens the credibility of the argument. It is often used in constructions like “perustellusti voidaan todeta” (it can be stated/concluded in a justified manner) or “hän puolusti kantansa perustellusti” (he defended his stance with justification).

Examples include: “Perustellusti voidaan todeta, että investointi tuottaa pitkällä aikavälillä hyötyä.” and “Hänen päätöksensä perustellasti huomioi sekä taloudelliset että eettiset näkökulmat.” In usage, it is common to pair the adverb with references to evidence, data, or logical reasoning.

See also: perustella, perusta, perustelu, perustelut. Note that perustellisesti is different from perusteellisesti, which means “thoroughly”; the two should not be conflated.