cerium

Cerium is a rare-earth element primarily recognized for its role in industrial chemistry. It is most commonly encountered in the context of catalytic converters, where it helps manage exhaust emissions, and in the production of lighter flints due to its pyrophoric properties.

As a chemical element, it is treated as an uncountable mass noun. It refers to the substance in general rather than individual atoms or discrete objects, meaning it does not have a plural form in standard scientific or general usage.