(1):

(n.) The act of demonstrating; an exhibition; proof; especially, proof beyond the possibility of doubt; indubitable evidence, to the senses or reason.

(2):

(n.) An expression, as of the feelings, by outward signs; a manifestation; a show.

(3):

(n.) The exhibition and explanation of a dissection or other anatomical preparation.

(4):

(n.) (Mil.) a decisive exhibition of force, or a movement indicating an attack.

(5):

(n.) The act of proving by the syllogistic process, or the proof itself.

(6):

(n.) A course of reasoning showing that a certain result is a necessary consequence of assumed premises; - these premises being definitions, axioms, and previously established propositions.