It's seems easier to define what true is. A truth is a true statement.
One way to define true is as a quality of a statement. It is a case of having a statement which is deducible from prior true statements. But a true statement can also be assumed true without being shown true from prior statements - but from which no contradiction to other true statements can be deduced.
Logically, I think of a true statement only as it is true in relationship to other statements. And a statement can be true with regard to one statement, and false with regard to another. In that sense, the truth of a statement is relative. Is it true to with respect to reality, experience, Scripture, intuition, the axioms of Euclidean geometry, the story line of the Hobbit?