They might have the same meaning, but do have different usage nowadays. ### 世间 ### **the world around people** It focuses on people or human and express in an emotional way. `这世间每天有许多事发生` means `lots happening around you` (or in your life). Also often used in chinese literary works (or classic style literary). `世间所有的相遇,都是久别重逢` (feels odd with `世界`) ------------- ### 世界 ### **time and space (on the earth or in novel)** It appears more objective or formal and can be used in academic or formal writing. `世界上有成千上万的生物`, millions of creatures living in the world `吉尼斯世界记录`, Guinness World Records `魔戒发生在中土世界`, The Lord of the Rings happened in Middle-earth