标 (biāo) is a versatile verb meaning 'to mark, label, or indicate' — it's the core single-character word for marking. Its two-character synonyms 标识 (biāo shí) and 标示 (biāo shì) are more formal: 标识 often refers to a logo or sign, while 标示 focuses on clearly indicating something. 标 also has a distinct sense 'to bid (for a contract)', which the compounds do not share.