空白 (kòng bái) literally combines 空 (kòng), meaning 'empty' or 'vacant', and 白 (bái), meaning 'white'. Together, they form a noun meaning 'blank space'—as in an empty area on paper, a screen, or a form—or figuratively 'a vacancy' or 'gap', such as in schedules, knowledge, or experience. It often refers to something that is intentionally or unintentionally left unfilled.

This word appears frequently in everyday contexts: filling out forms (e.g., 'fill in the blank spaces'), describing unused time ('a gap in your schedule'), or highlighting missing information ('a gap in our understanding'). Unlike the adjective 空白 (kōng bái)—which means 'blank' or 'void' and uses the first tone on 空—this noun form always uses the fourth tone (kòng) on 空. It’s neutral in register and common in both written and spoken Mandarin.