Children are extremely gifted in acquiring their native languages, but languages nevertheless change over time. Why does this paradox exist? In this course, we address this question by studying pidgin and creole languages. More precisely, we examine how, in a situation of contact, syntactic and semantic features of different language types or varieties may recombine into a new emergent linguistic system. Though much of the discussion will be based on pidgin and the Atlantic creole languages for expository reasons, the term contact is taken to mean the competition between idiolects (or variants) of the same language or the competition between (genetically and typologically) different languages. Under this view therefore, both L1 acquisition and L2 acquisition involve language contact, though the two processes differ qualitatively. Issues of age aside, one such difference is that L1 acquisition necessarily involves contact of dialects or closely related variants of the same language. In this case we are dealing with varieties that are genetically and typologically related. L2 acquisition, on the other hand, may involve two or more distinct languages not necessarily genetically or typologically related. Thus any learner, whether L1 or L2, finds herself in a situation of linguistic contact, in which she learns to master multiple linguistic sub-systems that may be combined to produce new variants. Accordingly, every situation of acquisition leads to the development of a hybrid grammar. Pidgin and creole languages represent a very rich empirical domain for investigating how language contact proceeds and how competition between different variants may lead to the emergence of a new grammar.