Definition of paradox:

(logic) a statement that contradicts itself

Synonyms of paradox:

absurdity, enigma, contradiction, inconsistency, puzzle, mystery, riddle, irony, dilemma

Opposite/Antonyms of paradox:

certainty, axiom, explanation, normality, proposition, fact, certitude, answer, regularity, standard, accuracy, correction

Sentence/Example of paradox:

The difference, however, between a paradox of terms and an aporia of terms lies in difference itself.