沙发椅 (shā fā yǐ) literally combines 沙发 (shā fā, 'sofa') and 椅 (yǐ, 'chair'), referring specifically to a single-seat, upholstered armchair—often with side arms and cushioned backrest—designed for comfort and relaxation. Unlike a standard chair (椅子), a 沙发椅 emphasizes softness, support, and lounging functionality, and is commonly found in living rooms, studies, or hotel lobbies.

The term reflects Chinese lexical borrowing: 沙发 is a phonetic loanword from English 'sofa', while 椅 adds the semantic category of seating furniture. Though sometimes used interchangeably with 单人沙发 (dān rén shā fā, 'single-person sofa'), 沙发椅 more precisely denotes an armchair rather than a compact sofa. It’s a neutral, everyday term suitable for both spoken and written contexts, especially when distinguishing seating types in home furnishing or interior descriptions.