In Latin, Caius is an archaic spelling of the Latin praenomen Gaius, pronounced /ga:ius/.
In early Latin, the letter C was used for both /g/ and /k/; and the names Gaius and Gnaeus were spelt Caius and Cnaius and continued to be so in inscriptions, after the letter G was introduced, and C was confined to the /k/ sound.
Notably, the name of Gaius Iulius Caesar is abbreviated CIC.
In English, Caius is a latinized spelling of the last name of John Keys of Gonville and Caius College, Cambridge.
Caius may refer to: