The Yangtze is the great river of China — the longest river in Asia, about 6,300 km, running from the Tibetan Plateau all the way east to the sea near Shanghai. In English it is almost always "the Yangtze" or "the Yangtze River", with "the" in front, the way English does with rivers. Two things often surprise students. First, this is a place name in geography books, news reports, and travel writing, so it appears in fairly formal English; you will not hear it in daily chat unless the topic is China. Second, and more interesting: Chinese people do not call it this. In Chinese the river is 長江. "Yangtze" comes from 揚子, which was only the name of a small part of the river near Yangzhou, close to a ferry crossing called 揚子津. Foreign visitors heard that local name, thought it was the name of the whole river, and carried it home. So the English name is a piece of the river standing in for all of it — a common accident with place names. You may also meet the old story that Yangtze means "son of the ocean", from 洋子江. That is a folk etymology: a wrong-but-pretty explanation people repeated because it sounded good. Chinese speakers writing careful English sometimes prefer "the Changjiang", but "the Yangtze" is what most English readers know.