a tentative theory about the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; "a scientific hypothesis that survives experimental testing becomes a scientific theory"; "he proposed a fresh theory of alkalis that later was accepted in chemical practices"
a proposal intended to explain certain facts or observations
the speech act of answering an attack on your assertions; "his refutation of the charges was short and persuasive"; "in defense he said the other man started it"
a formal public statement; "the government made an announcement about changes in the drug war"; "a declaration of independence"
a public statement about something that is happening or going to happen; "the announcement appeared in the local newspaper"; "the promulgation was written in English"