The Chinese word 必定 (bìdìng), meaning "certainly" or "definitely", is formed through the compounding of two semantically related characters: 必 (bì), which means "must" or "necessarily", and 定 (dìng), which means "fixed", "settled", or "decided". This combination follows a common pattern in Chinese word formation where two characters with similar or reinforcing meanings are joined to create a single, more emphatic concept. In this case, both components convey notions of inevitability and resoluteness, so together they form an adverb that intensifies the sense of certainty, essentially meaning "must and definitely so". This type of construction, known as a coordinative compound, strengthens the overall meaning by layering synonymous ideas.