Sentence:  Inversion is the inferring, from a given proposition, another proposition whose subject is the contradictory of the subject of the original proposition. The given proposition is called the Invertend, that which is inferred from it is termed the <WSD>Inverse</WSD>... The rule for Inversion is: Convert either the Obverted Converse or the Obverted Contrapositive. 
Meaning of the word marked with <WSD> tags:  The non-truth-preserving proposition constructed by negating both the premise and conclusion of an initially given proposition.