tõestanud

Tõestanud is an Estonian past active participle and a verbal form of the verb tõestama, meaning "to prove" or "to demonstrate". As a participle it conveys that the subject has performed the action (e.g., "ta on tõestanud" — "he/she has proven"). The form is created by adding the -nud suffix to the verb stem, a regular pattern in Estonian for forming perfect participles.

Grammatically, tõestanud can function both as part of compound verb tenses (used with auxiliary olla to form the perfect) and as an adjectival participle that agrees with nouns in case and number. It contrasts with the passive participle tõestatud, which denotes that something has been proven by an unspecified agent. Common related lexical items include tõestama (verb), tõestus (proof) and tõend (evidence).

Usage spans everyday, legal and scientific contexts, appearing in expressions about demonstrated facts, proven theorems or established evidence. The word is cognate in meaning to Finnic forms such as Finnish todistaa (verb), reflecting shared Finno-Ugric roots for the concept of proof and demonstration.