petro-

Also petri‑.

Rocks; petroleum.

Greek petros, stone, petra, rock.

To petrify something is literally to turn it into stone, though it is more frequently used figuratively to refer to somebody so frightened that they are unable to move or think; a petroglyph (Greek glyphē, carving) is a rock carving, especially a prehistoric one; petrography is the systematic description of the composition and properties of rocks based on observation; petrology is the study of rocks, including their origins, structure, and composition

Petroleum derives from Latin oleum, oil. A number of terms in petro‑ refer to petroleum, for example petrochemicals, substances obtained by the refining and processing of petroleum or natural gas, and petrodollar, a notional unit of currency earned by a country from the export of petroleum.