X is the twenty-fourth letter in the modern Latin alphabet. Its name in English is spelled ex or occasionally ecks (pronounced /ɛks/), plural exes (pronounced /ɛksəz/).
The consonant cluster /ks/ was, in Ancient Greek, written as either Chi Χ (Western Greek) or Xi Ξ (Eastern Greek). In the end, Chi was standardized as /kʰ/ (/x/ in Modern Greek), while Xi was standardized for /ks/. But the Etruscans had taken over Χ from older Western Greek; therefore, it stood for /ks/ in Etruscan and Latin.