PIDGINS & CREOLES: Some Definitions

A lingua franca: is a language used by people whose mother tongues are different in order to communicate.

A Pidgin

• is a contact language or lingua franca that arose naturally (not like e.g. Esperanto) 
•  does not have native speakers
• is reduced in linguistic form and grammar
•  is restricted in contexts of use
•  is typically unstable and highly mixed
•   may sometimes be a stable variety with norms of acceptability,
•   but is NOT a fully adequate natural language.

Also, Pidgins:

• derive from the process of pidginization
• typically evolve from trade or plantation situations...
• ... where many languages occur but no one predominates;
• are the products of incomplete Second Language Acquisition, and thus...
• ... have small core vocabularies, and borrow extensively,
• ... have very surfacy grammar, much variation but little system,
• ... and sociolinguistically have no (or incoherent) norms of interpretation;
• have limited domains for expressive and communicative functions;
• typically either die out or evolve into creoles...
• ... through the process of creolization/nativization.

A Creole, on the other hand:

• does have native speakers
• has developed, thru expansion in linguistic form and grammar,
• and thru extension in use (communicative & expressive functions),
• into a full-fledged, complete and adequate natural language
• which is typically stable and autonomous in its norms

lso, Creoles:

• often evolve from pidgins, thru the creolization/nativization process;
• exist most often in post-colonial areas, where...
• ...they tend to be the vernacular of spontaneous daily use;
• are typically related to one widely-spoken language (often seen as a 'corruption' of it);
• are native languages acquired as mother tongues; thus...
• ...are products of First Language Acquisition, based on inadequate input (Bickerton);
• may either stabilize, decreolize thru contact, or die out
• may or may not be highly mixed, depending on their age & current language contacts;
• have established mechanisms for vocabulary extension (borrowing/integration rules);
• have less elaborate/grammaticalized structures in grammar than older languages do (whether standardized or not), but definitely more than pidgins;
• have much variation but coherent sociolinguistic norms (of evaluation/interpretation)
• have wider domains & are used more for expressive/communicative purposes...
• ... though they resemble non-standard dialects in terms of prestige;
• may remain stable over long periods or merge toward standard languages (decreolize).

Theories of Pidginization and Creolization:

divide up into those that are basically historical, versus those that are basically universalist. The basic facts they are both trying to explain are:

• why Creoles around the world, regardless of superstrate, are similar in structure (are they?)
• why Pidgins around the world, regardless of superstrate, are similar in structure (are they?)
• how and why Creoles and Pidgins are related:
• how they're similar, and how they're distinct
• how Creoles develop out of Pidgins (when and if they do)

Historical explanations:      

The basic idea is, most pidgins and creoles are the product of European colonialism going around the world and colliding with indigenous languages, often either enslaving their speakers or shipping them off to remote non-native areas to work as "indentured servants". So it originally seemed logical to try to explain as much as possible by common descent from the politically-dominant European "superstrate" languages and the "substrate" languages of the people they dominated - African languages in the Caribbean and the Indian Ocean, Austronesian and other languages in the Pacific, and so on - taking into account different social circumstances that obtain over such a period of extended contact, which typically result in development of pidgins early on, and creoles later on.

Input languages into Pidgins and Creoles are often referred to by the terms:

• Superstrate: a language spoken by people who held a socially dominant position in the contact that produced them.
• Substrate: a language spoken by people who held a socially subordinate position in the contact that produced them.
• Adstrate: another language involved that's neither in a dominant nor a subordinate situation (often one that came into contact after the initial situation applied).

 Source: http://privatewww.essex.ac.uk/~patrickp/Courses/PCs/IntroPidginsCreoles.htm