What’s the difference between an Inaccuracy, Miss, Mistake, and Blunder?


Inaccuracy: A poor (but not game-changing) move in a position where many better moves were available. Generally results in an evaluation change of around 1 point (e.g +2 to +0.8). It is also sometimes used for a losing move in a position that was already dead lost.
Mistake: A bad move that significantly alters the game. Generally results in the evaluation changing by around 3 points (e.g -2 to +0.5). A losing move in a position that was already very poor may also receive a "?". Additionally, common violations of opening principles (such as moving the same piece multiple times) are usually considered mistakes.
Blunder: Like a mistake, but significantly more devastating. Generally results in the evaluation changing by 4 or more points (e.g +2 to -5). Hanging a forced mate is almost always a blunder, with the exception of when the position was already losing or if it was a miss (see below)
Miss: A move that completely overlooks a much better one; usually the capture of a hanging piece, or a forced checkmate. A miss can rarely be a decent move in its own right, but more commonly it can also be a mistake or even a blunder.

Hmm.
I would have defined it like this:
An inaccuracy is just that, a subtle, small error, something that could have been done more optimally. A number of inaccuracies can definitely together change the end result.
A blunder is an obvious error. A single move that results in directly losing material. Unless the opponent misses it. The kind of error high rated players are no longer supposed to make. You can also blunder the game, i.e. blunder the king, i.e. blunder mate.
Mistake is just another word for error. In this context I would assume any error not a blunder or inaccuracy.
A miss is if you miss to capitalize on an opportunity, such as a blunder. AFAICS Here on chess.com they only count missed wins, i.e. if a move would have won the game.