1. Pastor ποιμήν
"Pastor" is Latin for "shepherd." It evokes images of tender—though sometimes tough—care for the "flock," the local congregation.
2. Elder πρεσβύτερος
The word translated "elder" sometimes is simply transliterated as "presbyter." Elder speaks of the authority of one that comes with age, maturity and seniority (whether literal or figurative). When spoken of in a ministerial sense physical age is not a consideration.
3. Bishop ἐπισκοπή
The King James translates this term as "bishop" though modern versions tend to use "overseer." It speaks of one who has the authority of supervision, of oversight. In early Christianity it spoke of pastors; as Christianity developed it then took on the meaning of a hierarchical ruler over pastors in a given district.
4. Ruler ἡγέομαι
Some may translate the Hebrew writer's Greek with an English noun, such as "leader" or "ruler." The Greek actually is in verbal form as shown by the King James Version:
Obey them that have the rule over you, and submit yourselves: for they watch for your souls, as they that must give account, that they may do it with joy, and not with grief: for that is unprofitable for you. (Hebrews 13:17)
It is important to note that all of these terms for the same office—that of pastor—are terms of authority. Far too often the American Church sees pastors as employees who are chaplains: those paid to marry 'em, bury 'em, visit 'em and comfort 'em but who have no real authority to command them. This is a grievous error and a woefully ignorant view in light of the New Testament.