Assertion. Something that is posited to be; propositions about empirical things and states of affairs that may be true or proven untrue: statements in text; arrays of entities and implied action in image; presences in space; existing objects; or presences in body, sound or speech.

Reference: Cope, Bill and Mary Kalantzis, 2020, Making Sense: Reference, Agency and Structure in a Grammar of Multimodal Meaning, Cambridge UK: Cambridge University Press, p. 241.