之间 (zhī jiān) is a noun meaning 'between, among, amid', always used after a noun or noun phrase (e.g., 朋友之间 'between friends'). It is more precise than 中间 (zhōng jiān), which can also mean 'the middle' of a physical space; 之间 focuses on the relationship or interval between two or more items. 之中 (zhī zhōng) is more literary and means 'within' or 'inside' a group or scope, while 之间 emphasizes the space between.