truth-n; 2 Senses

Sense Number 1: a proposition considered factual, an accurate statement

Commentary: TRUTH[+entity][+symbolic][+information][+proposition][+factual][+considered]
NOTE: may occur in the plural

I promise to tell the truth, the whole truth and nothing but the truth. (make honest statements)
We hold these truths to be self evident.
These truths of geometry are valid in a Euclidean space.

WordNet 3.0 Sense Numbers: 1, 3

Sense Number 2: a real state, not hypothetical

Commentary: TRUTH[+state][+real][-hypothetical]
NOTE: occurs only in the singular

The ugly truth of her husband's infidelity could no longer be ignored.
The politician was afraid they would find out the truth about his past.
The philosopher sought truth, beauty and goodness throughout his life.
The lawyer doubted the truth of the witness' statement. (Note: refers to the attribute of realness of the statement, not the statement itself - Sense 1)

WordNet 3.0 Sense Numbers: 2, 4