习俗 (xí sú) means 'custom' or 'tradition', especially local or cultural practices that are established over time. It is very similar to 风俗 (fēng sú), but 习俗 emphasizes the habitual practice itself, while 风俗 often refers to the broader social customs of a region. 传统 (chuán tǒng) is broader, covering traditions passed down through generations, including beliefs and values.