椅子 (yǐ zi) is a common noun meaning 'chair' — a piece of furniture with a seat, back, and usually four legs, designed for one person to sit on. The first character 椅 (yǐ) specifically refers to a backed seat, while the suffix 子 (zi) is a diminutive or nominalizing particle that turns the root into a concrete, countable object. Together, they form a standard, neutral term used in everyday contexts — from homes and offices to classrooms and restaurants.

This word is always used as a standalone noun and requires a measure word (e.g., 一把椅子 yì bǎ yǐzi) when quantified. It does not carry formal or informal connotations by itself, making it appropriate across registers. Unlike more specialized terms like 凳子 (dèngzi, 'stool') or 沙发 (shāfā, 'sofa'), 椅子 implies a distinct backrest and is rarely used metaphorically. It’s among the first furniture-related nouns learners encounter due to its high frequency and structural simplicity.