Caer (Welsh pronunciation: [kɑːɨr]; Old Welsh: cair or kair) is a placename element in Welsh meaning "stronghold", "fortress", or "citadel", roughly equivalent to an Old English suffix (-ceaster) now variously written as -caster, -cester, and -chester. In modern Welsh orthography, caer is usually written as a prefix, although it was formerly—particularly in Latin—written as a separate word. The Breton equivalent is kêr, which is present in many Breton placenames as the prefix Ker-.