Claudian letters
The Claudian letters were developed by, and named after, the Roman Emperor Claudius. He introduced three new letters to the Latin alphabet:
- Ↄ or ↃϹ/X to replace BS and PS, much as X stood in for CS and GS. 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, but 20th century philologists, working from copies of Priscian's books, believe it to instead resemble two linked Cs, 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. This letter should not be confused with the "open O" letter Ɔ.
- Ⅎ, a turned F or digamma to represent consonantal U. The minuscule form should not be confused with the IPA symbol representing a voiced palatal stop.
- Ⱶ, a half H. The value of this letter is unclear, but perhaps it represented the so-called sonus medius, a short vowel sound used before labial consonants in Latin words such as optumus/optimus. The letter was later used as a variant of y in inscriptions for short Greek upsilon. It may have disappeared because the sonus medius itself disappeared from spoken language.
Support for the letters was added in version 5.0.0 of Unicode. The letters are encoded as follows:
| Description | Letter | Unicode | HTML | Script |
| TURNED CAPITAL F TURNED SMALL F | Ⅎ ⅎ | U+2132 U+214E | Ⅎ ⅎ | Latin |
| ROMAN NUMERAL REVERSED ONE HUNDRED LATIN SMALL LETTER REVERSED C | Ↄ ↄ | U+2183 U+2184 | Ↄ ↄ | Latin |
| LATIN CAPITAL LETTER HALF H LATIN SMALL LETTER HALF H | Ⱶ ⱶ | U+2C75 U+2C76 | Ⱶ ⱶ | Latin |