διαθήκη properly, a disposition, i.e. (specially) a contract (especially a devisory will)Derivation: from G1303;KJV Usage: covenant, testament. G1303
Thayer:1) a disposition, arrangement, of any sort, which one wishes to be valid, the last disposition which one makes of his earthly possessions after his death, a testament or will 2) a compact, a covenant, a testament 2a) God's covenant with Noah, etc.
διαθήκη diathēkē dee-ath-ay'-kay From G1303; properly a disposition, that is, (specifically) a contract (especially a devisory will)KJV Usage: covenant, testament.