The word 盖子 (gàizi) is a compound noun formed through a common Mandarin morphological process where the meaningful root 盖 (gài), which conveys the core concept of "to cover" or "a lid," is combined with the nominal suffix 子 (zi). This suffix 子, when used in this grammatical context, typically serves to convert a verb or another root into a concrete, inanimate noun, thereby specifying and finalizing its meaning as "a cover" or "a lid." Thus, the formation creates a single, specific lexical item from a general action/object root and a functional, word-class-marking affix.