The word "头等舱" is formed by combining three characters: "头" meaning "head" or "first", "等" meaning "class" or "grade", and "舱" meaning "cabin". The characters are combined in sequence where "头等" together denotes "first-class", and adding "舱" specifies it as a cabin, thus creating the term for "first-class cabin". Each character contributes directly to the meaning, resulting in a compound that explicitly describes a premium compartment in transport.