Claudian letters

The Claudian letters were developed by the Roman emperor Claudius (reigned 41–54). He introduced three new letters to the Latin alphabet:

• Ↄ or ⵋ/X (antisigma) to replace BS [bz] and PS [ps], much as X stood in for CS [ks] and GS [gz]. The shape of this letter is disputed, however, since no inscription bearing it has been found. Franz Bücheler identified it with the variant Roman numeral Ↄ,^[2] but 20th-century philologists, working from copies of Priscian's books, believe it to instead resemble two linked Cs (Ↄ+Ϲ), which was a preexisting variant of Greek sigma, and easily mistaken for X by later writers. Revilo P. Oliver argued that Claudius would have based this letter upon the Arcadian variant of psi or .^[1] This letter should not be confused with the "open O" letter. (Ɔ)
• Ⅎ, a turned F or digamma (digamma inversum) to be used instead of the letter V when denoting the consonantal phoneme [w] or [β].^[2] Thus, it resembles the use of the letter V in modern Latin texts, where the vocalic use of the letter V is represented by its variant U, which has been recognized as a different letter only later.
• Ⱶ, a half H. The value of this letter is unclear, but it may have represented the so-called sonus medius, a short vowel sound (likely [ɨ] or [ʉ]) used before labial consonants in Latin words such as optumus and optimus. The letter was later used as a variant of [y] in inscriptions for short Greek upsilon (as in Olympicus). It may have disappeared because the sonus medius itself disappeared from spoken language.^{[1][citation needed]}