The Chinese word **机油** (jīyóu), meaning "engine oil" or "motor oil," is a compound noun formed through a straightforward modifier-noun structure common in modern Chinese. The first character **机** (jī) is a shortened form of **机器** (jīqì, "machine") or **发动机** (fādòngjī, "engine"), serving as the modifier to specify the type. The second character **油** (yóu) means "oil" or "lubricant," acting as the core noun. Thus, the combination **机油** literally translates to "machine-oil," specifically denoting the lubricant used in engines and machinery, illustrating how Chinese efficiently creates precise technical terms by combining meaningful semantic components.