The word **诚挚** (*chéngzhì*) is a compound adjective formed by combining two morphemes, **诚** (*chéng*), meaning "sincere" or "honest," and **挚** (*zhì*), meaning "earnest" or "profound." In Chinese morphology, this is a common coordinative or synonymous compounding structure, where two characters with closely related meanings are paired to reinforce and intensify a single concept—in this case, the quality of deep, heartfelt sincerity. The combination does not create a new, metaphorical meaning but instead merges the semantic fields of both characters to express a stronger, more formal, and emotionally weighted notion of genuine earnestness, often used in formal or written contexts like "诚挚的感谢" (sincere thanks).