尺子 (chǐ zi) is a common noun meaning 'ruler' or 'measuring stick' — a straight tool marked with units (usually centimeters and inches) used to measure length or draw straight lines. The first character, 尺 (chǐ), originally referred to an ancient Chinese unit of length (about 33 cm), and now also denotes rulers in general; the second character, 子 (zi), is a neutral diminutive suffix often attached to nouns to form concrete, everyday objects (like 桌子 zhuōzi 'table' or 筷子 kuàizi 'chopsticks'). Together, 尺子 emphasizes a physical, handheld measuring instrument rather than abstract measurement.

This word appears frequently in school, office, and craft settings — students use it for geometry homework, carpenters rely on longer versions, and artists select transparent plastic ones for precision. While 尺 alone can mean 'a unit of length' or be used in formal/technical contexts (e.g., 一尺 yī chǐ 'one chi'), 尺子 specifically refers to the object itself. It’s colloquial, universally understood, and never used metaphorically.