The Appendix Probi ("Probus' Appendix") is the conventional name for a series of five documents believed to have been copied in the seventh or eighth century in Bobbio, Italy. Its name derives from the fact that the documents were found attached to a copy of the Instituta Artium, a treatise named after (but probably not written by) the first-century grammarian Marcus Valerius Probus. The Appendix was likely composed in Rome around the first half of the fourth century AD. It is specifically the third of the five documents that has attracted scholarly attention, as it contains a list of 227 spelling mistakes, along with their corrections, which shed light on the phonological and grammatical changes that the local vernacular was experiencing in the early stages of its development into Romance. The text survives only in a carelessly transcribed water-damaged manuscript of the 7th or 8th century which is kept at the Biblioteca Nazionale Vittorio Emanuele III as MS Lat. 1 (formerly Vindobonensis 17).

Phenomena visible in the spelling mistakes

Note that the format is "[correct spelling], not [incorrect spelling]". Scribal abbreviations have been expanded.

Syncope

Development of yod from front vowels in hiatus

Change of to

Reduction of pretonic to

Loss of final

Loss of

Reduction of to

Loss of intervocalic before a back vowel

Confusion of and

Confusion of singletons and geminates

Elimination of imparisyllabic nouns

Adaptation of 3rd-decl. adjectives to the 1st class

Adaptation of 4th-decl. feminine nouns to the 1st decl.

Adaptation of 3rd/4th decl. feminines to the 1st decl. via diminutive suffix

Adaptation of neuter plural to the first declension

Elimination of the ablative

Alteration of nom. -es (in the third declension) to -is

=== Reduction of the endings -es and -is to -s ===

Loss of the masculine flexion -us

Metathesis, assimilation, dissimilation, etc.

Sources