theory Definition

a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena

a belief, policy, or procedure proposed or followed as the basis of action

an ideal or hypothetical set of facts, principles, or circumstances —often used in the phrase in theory

game theory

number theory

a theory of the nature of matter: all material substances are composed of minute particles or atoms of a comparatively small number of kinds and all the atoms of the same kind are uniform in size, weight, and other properties

any of several theories of the structure of the atom; especially : one based on experimentation and theoretical considerations holding that the atom is composed essentially of a small positively charged comparatively heavy nucleus surrounded by a comparatively large arrangement of electrons

a view of filmmaking in which the director is considered the primary creative force in a motion picture

a theory in astronomy: the universe originated billions of years ago in a rapid expansion from a single point of nearly infinite energy density

a theory in early quantum physics: an atom consists of a positively charged nucleus about which revolves one or more electrons of quantized energy

mathematical theory and conjecture that uses topology to explain events (such as an earthquake or a stock market crash) characterized by major abrupt changes

a theory in biology that includes one or both of the statements that the cell is the fundamental structural and functional unit of living matter and that the organism is composed of autonomous cells with its properties being the sum of those of its cells

a branch of mathematical and physical theory that deals with the nature and consequences of chaos and chaotic systems