theories

noun, plural the·o·ries.

1. a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena: Einstein’s theory of relativity.
2. a proposed explanation whose status is still conjectural and subject to experimentation, in contrast to well-established propositions that are regarded as reporting matters of actual fact.
3. Mathematics. a body of principles, theorems, or the like, belonging to one subject: number theory.
4. the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory.
5. a particular conception or view of something to be done or of the method of doing it; a system of rules or principles: conflicting theories of how children best learn to read.
6. contemplation or speculation: the theory that there is life on other planets.
7. guess or conjecture: My theory is that he never stops to think words have consequences.

Idioms

8. in theory, ideally; hypothetically: In theory, mapping the human genome may lead to thousands of cures.

noun plural -ries

1. a system of rules, procedures, and assumptions used to produce a result
2. abstract knowledge or reasoning
3. a speculative or conjectural view or ideaI have a theory about that
4. an ideal or hypothetical situation (esp in the phrase in theory)
5. a set of hypotheses related by logical or mathematical arguments to explain and predict a wide variety of connected phenomena in general termsthe theory of relativity
6. a nontechnical name for hypothesis (def. 1)

n.1590s, “conception, mental scheme,” from Late Latin theoria (Jerome), from Greek theoria “contemplation, speculation, a looking at, things looked at,” from theorein “to consider, speculate, look at,” from theoros “spectator,” from thea “a view” + horan “to see” (see warrant (n.)). Sense of “principles or methods of a science or art (rather than its practice)” is first recorded 1610s. That of “an explanation based on observation and reasoning” is from 1630s. n.

1. A systematically organized body of knowledge applicable in a relatively wide variety of circumstances, especially a system of assumptions, accepted principles, and rules of procedure devised to analyze, predict, or otherwise explain the nature or behavior of a specified set of phenomena.
2. Abstract reasoning; speculation.

1. A set of statements or principles devised to explain a group of facts or phenomena. Most theories that are accepted by scientists have been repeatedly tested by experiments and can be used to make predictions about natural phenomena. See Note at hypothesis.

In science, an explanation or model that covers a substantial group of occurrences in nature and has been confirmed by a substantial number of experiments and observations. A theory is more general and better verified than a hypothesis. (See Big Bang theory, evolution, and relativity.)