The word "αδάμας" in ancient Greek is an adjective which means "undivided", "indestructible" "undefeated".
The precious stone took its name from this adjective because of its property( indestructibility).
So, "αδάμας" (or "διαμάντι" in modern Greek) also means "diamond".
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Vasiliki Baskou, Instructor/Director, https://learn-greek-online.com.