The word 阶级 (jiējí), meaning "social class," is formed through semantic compounding, where two independent characters with related meanings combine to create a new, more specific concept. The character 阶 originally refers to "steps" or "stairs," implying levels or tiers, while 级 means "grade" or "rank." Together, they construct a metaphorical meaning of hierarchical stratification, directly visualizing the idea of different graded levels within a social structure, which was then extended from its architectural roots to describe socio-economic rankings in society.