“A theory is an explanation of some aspect of the natural world that's well-substantiated by facts, tested hypotheses, and laws.”

A theory is constructed out of concepts, which are referenced with words within a language.

References

Hamer, A. What’s the difference between a fact, a hypothesis, a theory, and a law of science? https://www.discovery.com/science/Difference-Between-Fact-Hypothesis-Theory-Law-Science