CJK is the abbreviation of Chinese, Japanese, and Korean languages. These three languages are geographically close. But do they have something else in common?
Chinese is a Sino-Tibetan language. Japanese belongs to a Japonic language family. And Korean is a language isolate. Japanese might be related to Korean, but it’s not sure.
One thing is common, though. They all use chinese characters: hanzi (Chinese) or kanji (Japanese) or hanja (Korean). In Korean chinese characters are used less frequently.