It is a Portuguese-based creole language different from other Portuguese-based creole languages in Africa. The main difference is the substrate form Kimbundu and Kikongo from Angola.1
In the middle of the 16th century, a slave ship from Angola sunk before the southern coast of São Tomé. The surviving people aboard settled the coast as free fishermen. Their language was different from other creole language on the island. Today, between 10% and 20% of its linguistic elements are still of African origin.2
European Portuguese is mostly spoken in formal situations, in the media, business, education, judicial system and legislature, while Angolar and Sao Tomean Portuguese are preferred for informal situations as a vernacular language in day-to-day life and daily activities, and code switching even occurs between Angolar, standard European Portuguese, and São Tomean Portuguese in informal speech.
Lorenzino, Gerardo A. (1998). The Angolar Creole Portuguese of São Tomé : its grammar and sociolinguistic history. München: LINCOM Europa. ISBN 978-3895865459. 978-3895865459 ↩
Christóvão, Fernando, ed. (2005). Dicionário temático da Lusofonia (1 ed.). Lissabon/Luanda/Praia/Maputo: ACLUS. p. 614. ISBN 972-47-2935-4. 972-47-2935-4 ↩