(of a verb, adjective, or noun phrase) presupposing the truth of an embedded sentence that serves as complement, as realize in I didn't realize that he had left, which presupposes that it is true that he had left.
a factive expression.
Origin of factive
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logic linguistics philosophy (of a linguistic context) giving rise to the presupposition that a sentence occurring in that context is true, as John regrets that Mary did not attend
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012