a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena

a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena

a belief that can guide behavior

(chemistry) theory that describes aqueous solutions in terms of acids (which dissociate to give hydrogen ions) and bases (which dissociate to give hydroxyl ions); the product of an acid and a base is a salt and water

(chemistry) theory that describes aqueous solutions in terms of acids (which dissociate to give hydrogen ions) and bases (which dissociate to give hydroxyl ions); the product of an acid and a base is a salt and water

(biology) a scientific theory of the origin of species of plants and animals

(economics) a theory of competition stated in terms of gains and losses among opposing players

(physics) the theory that any two particles of matter attract one another with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them

(physics) the theory that any two particles of matter attract one another with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them

(chemistry) the theory that all indicators are either weak acids or weak bases in which the color of the ionized form is different from the color before dissociation

(biology) a theory of how characteristics of one generation are derived from earlier generations

(biology) a scientific theory of the origin of species of plants and animals

a theory (popular in the 18th century and now discredited) that an individual develops by simple enlargement of a tiny fully formed organism (a homunculus) that exists in the germ cell

the branch of applied mathematics that deals with probabilities

a theory of evolution holding that evolutionary change in the fossil record came in fits and starts rather than in a steady process of slow change

(physics) the theory that space and time are relative concepts rather than absolute concepts

based in theory rather than experiment