清单 (qīngdān) is a noun meaning 'list, checklist' — a written or printed itemization, often used for shopping, tasks, or inventory. It is more specific than 目录 (mùlù, 'table of contents, catalog'), which organizes content in a book or directory. 单 (dān) alone can mean 'list' as a noun, but 清单 is the full compound for a detailed itemized list.