* ἑνότητα (henótēta): This is probably the closest single word translation and is often used. It emphasizes the state of being one or united.
* ένωση (énōsi): This word implies the act or process of uniting, or the state of being united, often in a more political or social context (e.g., the union of states).
* ομόνοια (omonoia): This translates more specifically to "harmony" or "unanimity," implying a unity of minds or wills.
The best choice depends on the context. If you can provide the sentence or context where you'd use "unity," I can offer a more precise translation.