Concise Bible Dictionary:
The two principal words in the New Testament translated “power” are 1. δύναμις, and 2. ἐξουσία. It is important to see the difference between them, for their signification is not at all the same. No. 1 may be described as “capacity, moral or physical ability, power.” No. 2 signifies “delegated authority, right, privilege, title.” The latter always supposes power to exercise the right; but in the former there is no thought of right or authority. No. 1 is translated in the AV “ability, might, mighty, mighty deeds, miracles, power, strength, violence, mighty works, wonderful works,” &c. which will help further to show the character of the word, contrasted with No. 2, which is translated “authority, jurisdiction, liberty, power, right, and strength.”
The word “power” occurs in both lists, and this needs to be cleared of any ambiguity. No. 2 is often translated “power” where some other word would convey the sense better; but there is no single word in the English language that exactly answers to the Greek, and which would suit in all places. A concordance must be consulted for a full list of the occurrences: a few passages only are cited. All “authority” is given to the Lord Jesus (Matt. 9:6; Matt. 28:18; John 17:2). Satan offered to give to the Lord “authority” over the kingdoms of the world which had been delivered to him, if the Lord would fall down and worship him (Luke 4:6). To as many as received the Lord, to them gave He “right” or “title” to become the children of God (John 1:12). “There is no ‘authority’ but of God.” No. 2 occurring five times in Romans 13:1-3. Along with ‘principality’ occurs No. 2 (Eph. 1:21; Eph. 3:10; Eph. 6:12; Col. 1:16; Col. 2:10, 15; Titus 3:1).
The principal thing to remember is that No. 2 signifies a delegated right or title, with the presumed power or strength to enforce the right; whereas in No. 1 it is strength or power only.
Strong’s Dictionary of Hebrew Words:
Meaning:
from 5810; forcible; collectively and concretely, an army