from 2900; to empower, i.e. (passively) increase in vigor:

KJV-- be strengthened, be (wax) strong.

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2900 krataios (krat-ah-yos');

from 2904; powerful:

KJV-- mighty.

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2904 kratos (krat'-os);

perhaps a primary word; vigor ["great"] (literally or figuratively):

KJV-- dominion, might [-ily], power, strength.