theory

n.

1. Principles

   law, principles, postulates, data, conditions, basis, plan, provision, ideas, formularization, systemization, system, codification, code, argument, plea, scheme, foundation, method, approach, outlook, doctrine, dogma, rationale, cosmology, Weltanschauung (German), philosophy; see also law 4.

2. Something to be proved

   hypothesis, assumption, conjecture, speculation, opinion; see also hypothesis, opinion 1.

theory, in scientific or technical use, refers to a general principle or set of principles, based on considerable evidence, formulated to explain the operation of certain phenomena the theory of evolution, though it is often loosely used to mean a mere conjecture, guess, or hypothesis; hypothesis refers to an explanation that is tentatively inferred, often as a basis for further experimentation, but that is not fully supported by evidence the nebular hypothesis; law implies an exact formulation of the principle operating in a sequence of events in nature, observed to occur with unvarying uniformity under the same conditions the law of the conservation of energy