Definitions

Clear-cut nomenclature is essential to clear thought.

B. H. Liddell Hart, Strategy

The truth or falsehood of all man's conclusions, inferences, thought and knowledge rests on the truth or falsehood of his definitions.

Ayn Rand

Art
Art is the selective re-creation of reality according to an artist's metaphysical value-judgements.

Ayn Rand, "The Psycho-Epistemology of Art"

Biology
Biology is the science that studies living organisms.

Andrew Layman

Definition
A definition is a statement the identifies the nature of the units subsumed under a concept.

Ayn Rand, "Definitions"

Education
Education is the systematic training of the conceptual faculty of the young by means of supplying in essentials both its content and method.

Leonard Peikoff, [extemporaneous, uneditted formulation]

History
History is the science that studies what man has done, identifying fundamental causes.

Eric Daniels

Life
Life is a process of self-sustaining and self-generated action.

Ayn Rand, Galt's speech.

Literature
Literature is the branch of art which recreates reality by means of language.

Ayn Rand, "Art and Cognition"

Natural Science
Natural Science is the branch of science that studies all phenomena except those dependent on the action of man's conceptual consciousness.

Andrew Layman

Philosophy
Philosophy is the science that studies the fundamental nature of existence, of man and of man's relation to existence.

Ayn Rand,

Science
Science is the systematic knowledge gained by use of reason based on observation.

Leonard Peikoff, "Virtue as Practical"

War
War is armed conflict among men, in which a political unit attempts to achieve objectives by means of organized force against other men.

Andrew Layman

Vitruvian Man, by Leonardo da Vinci

Vitruvian Man, by Leonardo da Vinci