You are right that authority and power are usually synonymous. But if a distinction were to be drawn, I would say that the opinions of a person having authority would be respected by other intelligent and educated people, but the authoritative person could not enforce that respect. Persons having power, on the other hand, can force others to respect and comply with their opinions.
Thank you for your explanation. I understand it. Another similar word comes to mind - authoritarian. I have usually come across this word in the term 'authoritarian regime'. I think in case of an authoritarian regime, not only do they have power, but they can force others to comply. In contrast, a Prime Minister or President may have power, but they may not be authoritarian. Am I right in using these words like this?
Since this post is about 'authority', I am editing my reply to include a related word that I came across today -
panjandrum
The sentence I came across was - "Bill Gates might call Microsoft people and say hello how are you what are you doing for Microsoft today, but
The Director of Collegiate Education is a grand panjandrum, sits inside a stone building that was once some royal’s property in British days, now guarded by several watchmen, within acres of garden, his office tended to by a secretary and several support staff, their office surrounded by several rooms where minions sit typing, pushing files and shepherding courses, careers and years of dust."
I looked up the meaning and freedictionary.com says:
"pan·jan·drum (p
n-j
n
dr
m)
n. An important or self-important person: "a panjandrum of the publishing business" (Nat Hentoff).
[After the Grand Panjandrum, a character in a nonsense farrago written by Samuel Foote (1720-1777).]"