Demonstration \Dem`on*stra"tion\, n. [L. demonstratio: cf. F. d['e]monstration.]

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

Those intervening ideas which serve to show the agreement of any two others are called ``proofs;'' and where agreement or disagreement is by this means plainly and clearly perceived, it is called demonstration. --Locke.

2. An expression, as of the feelings, by outward signs; a manifestation; a show.

Did your letters pierce the queen to any demonstration of grief? --Shak.

Loyal demonstrations toward the prince. --Prescott.

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

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

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

6. (Math.) 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.

Direct, or Positive, demonstration (Logic & Math.), one in which the correct conclusion is the immediate sequence of reasoning from axiomatic or established premises; -- opposed to

Indirect, or Negative, demonstration (called also reductio ad absurdum), in which the correct conclusion is an inference from the demonstration that any other hypothesis must be incorrect.

Source: Webster's Revised Unabridged Dictionary (1913)