330px|right|thumb|Claudian letters, with the [[File:Claudian antisigma.svg|15x15 px variant of supported by manuscripts of Priscian. 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 .
As noted, no examples of this letter from the time have been discovered; its usage must be guessed at. It would probably replace the PS or BS sequence in Latin words, especially those with Greek etymology, such as (), (), (), or ().
<span class="anchor" id="Digamma inversum"></span> (Ⅎ)
Ⅎ, a turned F or digamma () to be used instead of the letter V when denoting the consonantal phoneme or .
<span class="anchor" id="Half H"></span>Half H (Ⱶ)
Ⱶ, a half H, probably had the name in harmony with other vowels. The value of this letter is unclear, but it may have represented the so-called , a short vowel sound, likely , but it could have also been . It was used before labial consonants in Latin words such as and . The letter was later used as a variant of in inscriptions for short Greek upsilon (as in ). It may have disappeared because the itself disappeared from spoken language.
Usage
These letters were used to a small extent on public inscriptions dating from Claudius' reign, but their use was abandoned after his death. Their forms were probably chosen to ease the transition, as they could be made from templates for existing letters. He may have been inspired by his ancestor Appius Claudius the Censor, who made earlier changes to the Latin alphabet. Claudius did indeed introduce his letters during his own term as censor (47–48), using arguments preserved in the historian Tacitus' account of his reign, although the original proclamation is no longer extant. Suetonius said of Claudius' letters:
Assuming that the letters were added at the end of the alphabet, just like Y and Z were, and that the order of these 3 letters does not matter, the Latin alphabet with these letters would look like this:
{| class="wikitable" style="text-align:center"
|+ Classical Latin alphabet with the additional Claudian letters
|-
! style="text-align:left" | Letter
! A !! B !! C !! D !! E !! F !! G !! H !! I !! K !! L !! M !! N !! O !! P !! Q !! R !! S !! T !! V !! X !! Y !! Z !! Ↄ !! Ⅎ !! Ⱶ
|-
! style="text-align:left" | IPA
| |<br /> || || || || <br /> || || || || <br /><br /> || || || || || <br /> || || || || || || <br /> || <br /> || <br /> || || <br /> || ||
|}
Support for the letters was added in version 5.0.0 of Unicode. Although these letters, as all Latin letters in antiquity, originally occurred only in capital form, lowercase forms were introduced to meet Unicode casing requirements.