Truth is the marking down in words the agreement or disagreement of ideas as it is.
 John Locke, An Essay Concerning Human Understanding (1689). copy citation

Context

“But then it is they contain REAL TRUTH, when these signs are joined, as our ideas agree; and when our ideas are such as we know are capable of having an existence in nature: which in substances we cannot know, but by knowing that such have existed. 9. Truth and Falsehood in general. Truth is the marking down in words the agreement or disagreement of ideas as it is. Falsehood is the marking down in words the agreement or disagreement of ideas otherwise than it is. And so far as these ideas, thus marked by sounds, agree to their archetypes, so far only is the truth real.” source