That which corroborates.
The act of corroborating, strengthening, or confirming; addition of strength; confirmation
A proposition which is the contradictory of another proposition and which can be obtained from that other proposition by the appropriately placed addition/insertion of the word "not". (Or, in symbolic logic, by prepending that proposition with the symbol for the logical operator "not".)
A denial or contradiction.
The logical operation which obtains such (negated) propositions.
The act of negating something.