plural theories
Definition of theory
1
: a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena
the wave theory of light
2a
: a belief, policy, or procedure proposed or followed as the basis of action
her method is based on the theory that all children want to learn
b
: an ideal or hypothetical set of facts, principles, or circumstances
—often used in the phrase in theory in theory, we have always advocated freedom for all
3a
: a hypothesis assumed for the sake of argument or investigation
b
: an unproved assumption : conjecture
c
: a body of theorems presenting a concise systematic view of a subject
theory of equations
4
: the general or abstract principles of a body of fact, a science, or an art
music theory
5
: abstract thought : speculation
6
: the analysis of a set of facts in their relation to one another
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Merriam-Webster unabridged
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Time Traveler for theory
The first known use of theory was in 1592
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