Old South Arabian is a geographic term for four closely related languages spoken in the southern portion of the Arabian Peninsula. These languages are distinct from Classical Arabic, hence Old South Arabian and not Old South Arabic. The four languages are Sabaen, Minaen, Qatabanian, and Hadramitic.
OldSouthArabian (or Epigraphic SouthArabian) is the term used for four closely related languages spoken in the southern portion of the Arabian Peninsula.
OldSouthArabian had its own writing system, the SouthArabian alphabet, concurrently used for Ge'ez in the Ethiopian Kingdom of D`mt, ultimately sharing a common origin with the other Semitic abjads, the Proto-Sinaitic alphabet.
The arrival of Islam virtually disintegrated OldSouthArabian, as Classical Arabic became the lingua franca of the region.
The Arabic languages comprise North Arabic (or simply Arabic) and SouthArabian (or Himyaritic or South Arabic); SouthArabian differs sufficiently from North Arabic to be considered a separate language.
OldSouthArabian, or Himyaritic, was the language of people living in the S Arabian Peninsula in ancient times.
OldSouthArabian had its own alphabet, the origin of which is still not clear, although it is generally thought to have had the same source as the North Semitic writing.