Abstract concepts: Mathematical objects, Platonic forms, absolutes, universals, first principles, axioms, postulates, eternal truths, timeless truths, self-evident truths, absolute truths, necessary truths, a priori truths, analytic truths, synthetic a priori truths, tautologies, paradoxes, eternal realities, timeless realities, eternal essences, timeless essences, eternal forms, timeless forms, eternal archetypes, timeless archetypes, eternal ideals, timeless ideals, eternal values, timeless values, eternal virtues, timeless virtues
Concrete examples: Constants, invariants, timeless entities, eternal entities