世界 (sekai) means "world," "society," or "universe." You use it to refer to the Earth, the global community, or a particular sphere of activity or interest. It encompasses everything around us, from physical places to social environments. For example, 「世界中を旅行したいです。」 (I want to travel around the world.)

地球全体や、社会、ある特定の分野などを指します。「世界中を旅行したいです。」