The Chinese word **密度 (mìdù)**, meaning "density," is a compound noun formed through a common grammatical structure in modern Chinese where two meaningful characters (morphemes) combine to create a precise, specialized term. The first character, **密 (mì)**, means "dense," "close," or "thick," describing the state of matter packed tightly together. The second character, **度 (dù)**, means "degree," "measure," or "magnitude," and often functions as a suffix to form nouns indicating a measurable concept. Thus, **密度** literally translates to "the degree of denseness," which is the exact definition of density as mass per unit volume, demonstrating how Chinese efficiently constructs scientific terminology through logical semantic combination.