Perustuivatko

Perustuivatko is a Finnish verb form built from the verb perustua, meaning to be based on or to be founded on. It is the past tense, third-person plural form used in a yes–no question. In other words, perustuivatko asks whether something (they or some group) was based on a certain basis, or whether a decision, claim, or institution was founded on specific premises. The affirmative past form is perustuivat, while the interrogative form adds the question suffix -ko/-kö to the verb.

Grammatically, perustuivatko consists of the stem perustu- plus the plural ending -ivat and the interrogative suffix -ko. The -ko/-kö suffix is the Finnish question particle attached to the finite verb, and it does not require a separate inversion in simple yes–no questions. The phrase typically moves with a following expression specifying the basis, for example jostakin (based on something) or toisenlainen lähde (on another basis). The verb is intransitive and usually describes being based on evidence, data, or principles, rather than directly acting on an object.

Usage and context: perustuivatko is common in formal or written Finnish, including journalism, academia, and historical writing, when querying the basis of statements, decisions, or actions. It can pair with noun phrases in genitive to specify the basis, such as virheellisiin tietoihin (on false data) or aiempiin tutkimuksiin (on earlier studies). For example: Perustuivatko väitteet virheellisiin tietoihin? Perustuivatko päätökset taloudellisiin todisteisiin?

Etymology note: perustua comes from perust- (foundation) with typical verb-forming suffixes; perustuivatko is the interrogative past plural form.