And to quote one of the response which I couldn’t agree more:
"It’s much more of a cultural/linguistic thing
In Mandarin(MY Edit: and even in Cantonese), there is no generic word for ‘dumpling’. Every dumpling has its own individual name, be it a xiao long bao (soup dumpling), jian jiao (pan fried dumplings) or baozi (steamed soft bread bun filled with bbq pork or other fillings). Chinese people consider them all ‘dumplings’, in that they are all some kind of savory starchy thing filled with some kind of meaty/veggie thing.
Also, if you hang out with non-American Chinese people long enough, you’ll find that they don’t get all caught up in semantics. They don’t particularly care what it’s called, as long as it tastes good. (similarly, you’ll find that hardly any Chinese people use chopsticks the ‘correct’ way illustrated on the chopstick wrapper… they really don’t care, as long as it works)"
At best, 餃 is the closest there is to “dumpling” which encompasses many sort of closed as well as non-closed “dumplings”. Adding to the confusion, if you look up 餃 in a dictionary, the definition comes out as “stuffed dumpling; ravioli”.