assertion

1 a solemn and often public declaration of the truth or existence of something <the assertion that all men have certain unalienable rights is set forth in the Declaration of Independence> Synonyms affirmation, protestation, asseveration, avouchment, avowal, claim, declaration, insistence, professionRelated Words allegation; announcement, proclamation, pronouncement; argument, justification, rationalization, reason; confirmation, reaffirmation, reconfirmation, vindicationNear Antonyms disclaimer; challenge, dispute, question; confutation, disproof, rebuttal, refutation; contradiction, denial, negationAntonyms disavowal

2 an idea or opinion that is put forth in a discussion or debate <made the unlikely assertion that gravity affects light> Synonyms argument, contention, thesisRelated Words conjecture, guess, hunch, hypothesis, speculation, surmise, theory; proposal, proposition; assumption, presupposition, supposition; position, stand; case, explanation, rationale, reason