The topic is interesting in its own right. And I think that's important to keep in mind: A question that's General Reference doesn't have to be trivial or boring; it could be so compelling that it's caught the interest of many different people, laymen like myself and researchers alike.
And the answers to it are great! I always thought # was an odd symbol to connect with pound, but the images in your answer connecting it with a cursive "lb" are enlightening.
But I can see two interpretations of the question. And they vary over how easily they are answered by general references. I have a guess about which the asker meant, but I figure those who voted to close may have read the other meaning. I present them below.
Is there a difference between sharp sign and pound sign? Consider the original post:
What's the correct definition of the symbol "#"?
I'm used to say "Sharp sign" to make reference to # sign.
Today a friend told me that the correct "saying" is Number sign or Hash sign or even just Hash.
What is the difference between those "options" and what's the correct usage of the words for this sign?
It is unclear to me what the OP meant by those options. If OP is not asking for when to use sharp sign versus when to use number sign or hash sign or hash, then
- What is the purpose of the introductory sentence?
- Why use quotes around "Sharp sign" and "saying" if not to mark those as the also-quoted "options"?
- Why use correct in both the question title and in describing the friend's terms if not to ask "Is sharp sign also a valid name for #?"
If the incorrect term sharp sign for # has no bearing on OP's question, it might have been better to omit the first sentence entirely with something like
Today a friend told me that the way to say # is Number sign or Hash sign or even just Hash...
If OP wants to know the difference between sharp sign and number sign, the top entry of a Google search of sharp sign, OP's phrase of choice, addresses this:
The sharp symbol (♯) may be confused with the number (hash or pound) sign (#). Both signs have two sets of parallel double-lines. However, a correctly drawn sharp sign must have two slanted parallel lines which rise from left to right, to avoid being obscured by the staff lines. The number sign, in contrast, has two compulsory horizontal strokes in this place. In addition, while the sharp also always has two perfectly vertical lines, the number sign (#) may or may not contain perfectly vertical lines (according to typeface and writing style).
(Note: As I write this post, the above WP citation has a "citation needed" label. Although I hold its information to be true from my own experience, I would personally need a similar answer from another easily-available source before calling it General Reference.)
What is the most popular label for #? Judging from OP's comments and behavior, I think this is the intended question. OP wants to know a general, context-independent name for #, so the comment "Look a cloud shaped like a 'insert-correct-name' sign in the sky!" is easily understood and unambiguous. OP accepted the answer that went into depth about the derivation and typical context for each name of #, such as
The label pound sign used in weighing
[The name] pound sign... developed as a scribble for the abbreviation of pound in latin: lb, where lb is an abbreviation of libra, itself a shortened form of the full expression, libra pondo... If you look at how scribes scribbled lb, you might recognize the sign (in the first example) [example omitted] amongst the scribbled and attached lines.... That is still how it's scribbled: I do it myself when recording the weights of babies...
The label octothorpe used in the phone industry
... octothorp was coined by someone working for a phone company
The label hash tag in used in Information Technology
Hash tag ... in IT as a tag to group information.
and ended with the rule-of-thumb:
But from the 1300s, it has been known as the pound sign, or, in England, the number sign.
I do not consider the question answered here as General Reference.
But judging by what's presented in the question alone (disregarding information outside of it, such as OP's comments and my evaluations of OP's behavior) I understand why it might be closed as OT because of General Reference. Disagreements about what the name for # ought to be seem to me more indicative that the question interpreted is asking for opinions. Why does OP believe there ought to be a correct name? Does that imply other names for it are incorrect? What does OP mean by correct: popular, technical, general, original, or something else?
I think encouraging OP to clear up these gray areas would help remove the on-hold status the question now has.