Perustella

Perustella is a Finnish verb meaning to justify or substantiate an assertion by presenting grounds, reasons, or evidence. It involves showing how a claim or decision rests on certain bases, data, or principles. The word is built from the root perusta (to base; foundation) and the suffix -ella, and is closely related to the nouns peruste (basis, ground) and perustelu (justification).

Usage and grammar: It is a transitive verb that takes a direct object representing what is being justified, such as väite (claim), päätös (decision), or näkökulma (viewpoint). Common constructions include perustella väitteensä (to justify one’s claim) and perustella päätöksensä (to justify one’s decision). It can also be used with questions to form perustele miksi... (justify why...), and it appears in the passive-like adjective form perusteltu, meaning justified, as in päätös on perusteltu.

Context and nuance: In formal writing, especially in academic, legal, or policy contexts, perustella emphasizes providing explicit grounds and evidence for a conclusion. In everyday language, speakers may use synonyms such as selittää (explain) or antaa perusteet, but peruste in these phrases remains central to indicating justification. Related terms include peruste (basis), perusteet (grounds), and perustelu (rationale).