The Queen's Gambit is not a gambit. Change my mind.

It's not a real gambit because you can always get back your pawn, and if you'll do that, you won't lose anything (if you did it in other gambits, you would lose the advantage).

I've never played this opening, and my opinion may be wrong. I hope you can explain to me why they consider this opening as a gambit.

Why do they believe that it's a gambit when someone can always get back their pawn?
In the King's / Halloween / Italian / Wing Gambit you don't have such an opportunity.

I believe this is called a sound gambit. Gambits don’t always have to be unnecessarily risky or dangerous. They’re simply a sacrifice of a pawn or piece in exchange for a better position, not always a wild trap. 

correct, the queen's gambit isn't really a gambit

I play this opening a lot and there is a lot of joking with whether or not this opening is a gambit or not. Clearly, it "sacrifices" a pawn and therefore it was named a "gambit" back when the opening was first discovered and named (pre-1600 since that is when Greco was studying openings like this in his games collection; btw, I mean pre YEAR 1600 and not rating )

Modern consensus has been that the Queen's Gambit is not a "true gambit" since the pawn can always be won back (or a larger advantage via initiative or other compensation if White plays optimally while letting Black keep the "extra" pawn).

Now we get into the debate of what defines a "gambit" opening. It isn't how sound it is...is it? Some "gambit" openings seem to be getting a reputation that they are sound; should we change the names for those openings? If one defines a "gambit" purely by offering material...then 2. c4 offers material and the Queen's Gambit should be called a gambit. 

I just consider this opening a "gambit", but not a "true gambit" (connotation of being an unsound sacrifice attempting to catch the unprepared xD)

I think it’s safe to say there’s a large range of gambits

In terms of the kind of compensation you get

In the QGA, black gets more activity than in the QGD. What white gets is the centre. The QGA isn't a true gambit although white and black can play it as a gambit. For instance, 1. d4 ...d5 2. c4 ...cd 3. Nf3 ... c6 4. e4 ...b5 or 3. Nc3 ...a6 4. e4 ... b5 are possible lines which are gambit-like.

You're right lol

tails u kinda annoying tbh

White can reclaim the pawn, but in some lines, black can greatly improve his position while white burns time trying to win the pawn back.

Example:

White won the "gambit" pawn back. But now black has connected passed pawns on the a and b files.

White has to play with care, or black will steamroll over him.

even if it's not the endgame, black can still push the a- and b-pawns very soon, and white has to be very careful 

Generally, when black plays lines which hold the pawn for a few moves and white plays e4, it can become a genuine gambit because it's the e4 pawn that can drop. I usually play 3. Nf3 and 4. e3. 3.e3 is the easiest way to get back the pawn but black can't hold it after 3. Nf3 and 4 e3, even if white has to take on c4 and then play Qa4+ to get the piece back. Usually the Q side is bust open with a4 and b3, and white can get a lot of play there. I like playing against the QGA and also sometimes play it as black.

The lines you're talking about, such as the Noteboom, are theoretically equal but VERY unbalanced.

I was bust by that move in a tournament. It was a five round weekend major. Either under 1800 or under 1880 (FIDE). I was on three and a half out of four but there were about seven players just behind me and one equal. I had black and I had to win to win the tournament outright, because a draw could have meant a five or six way tie. It was the days before I'd switched from the QGA to the Modern Benoni. It was actually the reason I switched. I was tired and my opponent was experienced. He played 3. e3 and, like s complete fool, I played 3. ...e5 and was positionally outplayed in a queenless middlegame. Looking at it later, the entire thing was better for white, it turned out. I lost and was out of the prizes altogether but in those days I played more for the money than anything else and I was gambling the £150 first prize, in the days when the entry fee was £6, against about £40 if I drew.

still not so simple though, because black will bring pieces to the queenside, and the lsb alone will not be enough if you get too carried away in the center and kingside

Good explanation! Yes, this name is determined only by an old (and wrong) tradition. And perhaps the title "Queen's Gambit" would have sounded appropriate five hundred years ago, but now it is completely irrelevant. It's definitely not a real gambit, but it's a gambit nonetheless, haha.