The correct word similar in meaning to "prosperity" is "multiplicity". Prosperity refers to wealth, success, or thriving conditions, and multiplicity refers to a large number or variety, which is often a sign of flourishing or prosperity.
- Journaleese refers to a specialized jargon used in journalism.
- Postulate refers to a statement assumed without proof, unrelated to prosperity.
- Convexity refers to the property of being curved outward.
Thus, the correct answer is "multiplicity".