两术语均有法律事务“代理人”的含义，attorney-at-law主要指具有律师资格[1]，且注册登记而从事法律事务代理者（licensed to practice law)。而attorney in fact则是指经授权委托书 (power of attorney)授权主要从事非诉讼活动者，多在庭外处理委托事务，其不一定必须具有律师资格[2] 。
 
[1]“A person who practice law; lawyer. ” Cf. Bryan A. Gamer, Black's Law Dictionary, 7th edition, at p. 802，West Group (1999).
[2] “An attorney who may or may not be a lawyer who is given written authority to act on another's behalf esp. by a power of attorney. " Cf. Linda Picard Wood, J. D. Merriam Webster's Dictionary of Law, at p. 38，Merriam-Webster, Incorporated Springfield, Massachusetts (1996).