中 (zhōng): Center, middle. This character is central to the name for China, `中国 (Zhōngguó)`, often translated as the “Middle Kingdom.”
国 (guó): Country, state, nation. A pictograph showing a boundary `囗` with jade `玉` inside, symbolizing the treasures or sovereignty within a nation's borders.
石 (shí): Rock, stone. A simple pictograph of a rock at the base of a cliff.
油 (yóu): Oil, grease. The left part is the water radical `氵`, indicating a liquid. The right part `由 (yóu)` provides the pronunciation.
How they combine: `中国 (Zhōngguó)` is the word for China. `石油 (shíyóu)` literally means “rock oil,” a direct and logical translation of “petroleum.” Put together, `中国石油` means “China Petroleum,” the formal name of this colossal national corporation.