ABSTRACT
Adults learning a second or foreign language often produce errors or nonnative substitutions, including a foreign accent and nonnative grammatical utterances (e.g., an English speaker who fails to master the Spanish trill and subjunctive verb constructions). Although a learner’s substitutions are often errors from the standpoint that they are not nativelike, they are representative of an underlying system, just as a child learning a first language has an underlying linguistic system, albeit different from adult native speakers of that language. For example, an adult French learner of English may substitute [z] for [ð] (the sound in the) but never [p], [b], [k], or [g]; the same learner may place the adjective after the noun (“I like that car green”) but not place it randomly elsewhere (*“I green like that car” *“I like green that car”). An adult second language learner’s linguistic system is termed the Interlanguage (IL) or simply the language of a nonnative speaker. 1
