Classical
Latin and vulgar Latin: Cases and Prepositions
In vulgar Latin AD + accusative replaced the dative:
MITTERE → AD + accusative
SCRIBERE → AD + accusative
DARE → AD + accusative
DICERE → AD + accusative
Dative case functions have nonetheless survived in Roumanian, and first declension singular forms also survive; even the vocative is retained.
In the West, the accusative/oblique case has dominated in the singular, whereas in the plural, nominative forms have survived.
When final S fell in Proto-Romance, a yod was sometimes left behind
e.g. CASAS > [kasaj] > [casej] > case
AMICOS > amici
GAUL:
Until the end of the twelfth century, Old French and Old Provençal observed both nominative and accusative cases:
MURUS, MURUM (sing.)
MURI, MUROS (plural)
Final M was lost, followed by the remaining final vowels. Only in the thirteenth century did 's' become settled as a plural maker in Gaul.
FRENCH, SPANISH, PORTUGUESE:
In French...
CÁNTOR > chántre
CANTÓREM > chantéur
Pairs of words survive. c.f. also pâtre, pasteur.
In Spanish...
MAESTRE < MAGÍSTER
→ 'master of' (mediaeval orders of chivalry)
MAESTRO < MAGISTRUM
Spanish nouns are usually derived from the accusative (or sometimes the genitive) case. The Latin nominative case is found, however, in occupations and names.
e.g. Dios < DEUS
The accusative form, Dio was used by the Jews because they did not accept the Holy Trinity. Occupations frequently appear in legal documents, which goes some way towards explaining the retention of the nominative:
preste < PRESBYTER
sastre < (sartre) < SARTOR
juez < JUDEX
The second s in sastre is the result of assimilation.
Forenames often figure in both legal and ecclesiastical documents:
MARCOS < MARCUS
PABLOS (mediaeval or dialectal)
MATÍAS
CARLOS ( KARL is germano-gallic,
but final S is retained in the English and French CHARLES.)
DOMINICUS: We have Dominic in English, Domingo in Spanish and Domingos in Portuguese.
Finally, the Latin nominative survives frequently in learned forms:
Júpiter
cráter
crisis
pendicitis
tórax
prefacio (Latin: PREFATIO)