Here you will discover not only the meaning of theory, but also the origin of the word, most used concepts. In addition, we will leave you some uses as an example so that you know how it is used in a sentence.

Definition of theory: What is it?

The most common definition of theory refers to a group of related ideas that reasonably explain a phenomenon. They are reasonable because they have been deduced from a hypothesis, and the consequent observation, experience and logic. The theory according to this meaning is reached through the scientific method.

This is another common definition of theory: it would be the group of norms, knowledge and notions that make up a doctrine, a system or a science. Normally, its use is reduced to doctrines that have a practical use, but it is not decisive.

Finally, we have perhaps the most colloquial use of the word. It refers to reasoning without scientific bases to explain an event or phenomenon. In this case it is more related to an assumption than anything else.


The word theory comes from the Greek θεωρία (theoría). Originally it specifically referred to a speculative thought. In turn, θεωρία has its roots in θεωρóς (theorós), which means “spectator”.

Aristotle speaks in The Poetics about the activities of man, and divided them into three fields: Πρᾱξις (praxis), practice, action. Ποίησις (poíesis), creation, poetic creation, realization. Θεωρία, knowledge, theory, search for truth.

Aristotle was precisely the first to propose the use of theory as a search for truth, beyond mere speculation.

Common uses

A word without context is just a word; it is enough that a context is added for it to acquire multiple meanings. So according to the different definitions of theory today, we have put together a group of examples that can help you understand it better.

As for the first use, which we will qualify as “scientific”, we can apply it to refer, for example, to Einstein's theory of relativity. We would also find Darwin's theory of evolution or, if we go deeper, Lewis's theory.

On the other hand, the second use, in which we would apply the word as a synonym of doctrine, we can find the color theory. We can also mention music theory, language theory, etc.

And finally, there is the “colloquial” use of the word, which refers more to speculation. And what better way to explain it than with examples?

“I have a theory that the neighbor is stealing the patio furniture.” “I was theorizing and I came to the conclusion that you are kidding me.”

Words similar to theory

We have made a small compilation of words similar to theory. You will find some that start from the same root teor-, and others that are related from a conceptual point of view.

  • Theoretical: Logically, it is correct and true, but it is not real because it remains on the plane of theory.

  • Theorem: Logical proposition whose truth is demonstrable. It is most often used in the field of mathematics.

  • A theorem is a proposition whose truth is proved. In mathematics, it is any proposition that, starting from an assumption, affirms a reasonableness that is not self-evident.

  • Hypothesis: Idea or assumption that comes out of certain data and often works as a foundation for a scientific investigation.

  • Conjecture: (subjective) opinion created thanks to incomplete data, assumptions or squalid clues

Antonyms of theory

Now let's review some of the antonyms of the word theory:

  • Praxis/practice: Application of a theory.

  • Pragmatism: In philosophy, a theory whose means of judging the truth is the observation of the consequences during its practical application.

  • Check: Go from theorizing to being certain of the truth. Basically, it is about putting theory into practice to demonstrate its validity.


Like all words, theory has undergone many changes since its appearance in the annals of history. In this particular case we can highlight its evolution from the simple observation of an object or phenomenon, to the scientific meaning. That is, rational, logical and well-founded observation, to help draw correct conclusions and reach the truth.


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