界 (pinyin: jiè, written "jie" or "jie") means boundary, limit; domain; society, the world. Below: its meaning, pronunciation, stroke order, and example sentences, so you can learn how to read, say, and write 界.
If you pass through a Chinese park in the morning, you'll often see a group of middle-aged and older people dancing or singing together. This kind of scene is not common in other parts of the world, but in China it has become a unique cultural phenomenon.