首席 (shǒu xí) literally combines 首 (shǒu), meaning 'head' or 'first', and 席 (xí), originally meaning 'mat' or 'seat'—historically, the most honored seat at a gathering. Together, they form a compound noun meaning 'chief' or 'principal', indicating the highest-ranking person in a professional or organizational role. It is commonly used before titles like conductor, scientist, engineer, or officer to denote top authority or seniority.

This term carries formal, respectful connotations and is frequently seen in institutional, corporate, academic, or artistic contexts—for example, 首席指挥 (chief conductor) or 首席科学家 (chief scientist). Unlike generic terms like 主要 (zhǔyào, 'main'), 首席 implies official designation and hierarchical precedence. It is rarely used alone without a following title and almost never in casual speech.