This is the OED definition
AD3
abbreviation
Anno Domini (used to indicate that a date comes the specified number of years after the traditional date of Christ's birth).
Before the Common Era (used of dates before the Christian era, especially by non-Christians).
If you want to assist someone in having a more informed opinion that is possible/ And you can dispute whther an opinion represents the known facts but you can't say an opinion is wrong. An opinion represent preferneces an as such can not be validated nor invalidated.
http://www.philosophersmag.com/essays/26-the-fact-opinion-distinction
“Facts are statements that can be shown to be true or can be proved, or something that really happened. You can look up facts in an encyclopedia or other reference, or see them for yourself. For example, it is a fact that broccoli is good for you (you can look this up in books about healthy diets).
“Opinions express how a person feels about something – opinions do not have to be based upon logical reasoning. For example, it is an opinion that broccoli tastes good (or bad).”
Both of these connect fact with provability. But in common parlance, “provability” seems audience-relative as well: While one person might find Anselm’s ontological argument to be a sufficient proof for God’s existence (thus rendering “God exists” a fact for that person); others may not.
The Education Oasis site announces that “An opinion expresses someone’s belief ... about something.” So if I believe that there’s beer in my refrigerator, is that just an opinion? The Enchanted Learning site muddies the waters even further by claiming that you can look up facts in an encyclopaedia (always? but then were there no facts before books?), and by including an evaluative notion (“good for you”) among examples of facts.
I therefore propose that we abandon the ambiguous fact/opinion distinction, and especially the dismissive retort “That’s just your opinion.” We should focus instead on whether people can offer good reasons for the claims they make – reasons that might compel us to share their views. That’s my opinion, anyway. If you think yours is better, don’t merely say so: Say why.