Now that we know the difference between a verb, a noun, an adjective, etc., let's take a look at a confusing issue.
We have two words in English that students often confuse. One is truth and the other is true.
Using them correctly is fairly easy once we realise that truth is a noun (which can be countable or uncountable) and true is an adjective.
In other words, something can be true (or its opposite, false) just as something can be black or white, large or small, beautiful or ugly.
Is the story about John true?
But we don't always use the adjective true. Sometimes we use the noun truth, as in the following examples:
Tell the truth. (Whatever you say should be true.)
I'm looking for the truth. (I want to find out what is true in this situation.)
Do you promise to tell the truth, the whole truth, and nothing but the truth, so help you God? (This is used in courts of law in the U.S. When the court "swears in" a witness, it wants that witness to talk about the incident in question--to say what is true, to leave nothing out, and not to add any false statements.)
We cannot say, Tell me the true, or This is a truth story, because we would be mixing up the functions of a noun and an adjective.