assertion

The act of asserting; positive declaration or averment.

Something which is asserted; a declaration; a statement asserted.

You're a man of strong assertions!

Suppose you are given the semifactual assertion, "even if Nora had liked mathematics then she would have became^([sic]) a scientist" and then you find out that Nora did in fact become a scientist.

A statement or declaration which lacks support or evidence.

That's just a bare assertion.

Drivers' union ASLEF bluntly rebuffed the claim of unofficial action, calling it a lie. And Avanti West Coast was unable to provide any proof for its assertion, when questioned by RAIL.

Maintenance; vindication.

the assertion of one's rights or prerogatives

A statement in a program asserting a condition expected to be true at a particular point, used in debugging.

The user should be absolutely confident that the error issued is a real design error. In other words, a user should be confident that his assertion code is correct and that the assertion failure is not a false condition.