The word 低于 (dīyú) is formed through a standard Chinese morphological process where the character 低 (dī), meaning "low", combines with the prepositional character 于 (yú), meaning "at; in; than". Together, they create a compound word that functions as a verb, meaning "to be lower than" or "to fall below". The structure follows a common pattern in Chinese where an adjective is paired with 于 to form a comparative phrase, literally translating to "low in/at/than", which grammatically indicates that the subject is inferior to a stated benchmark or standard, as in "温度低于零度" (The temperature is below zero degrees).