The term interlanguage is attributed to Larry Selinker (1972), who also coined the term fossilization. Interlanguage is a system of language that learners develop during L2 acquisition. It draws on aspects of the L1 and the target language, but it exists independently of either. The Center for Advanced Research on Language Acquisition (CARLA) refers to interlanguage as a “transitional linguistic system” that “can be described in terms of evolving linguistic patterns and norms, and explained in terms of specific cognitive and sociolinguistic processes that shape that system” (“Interlanguage”).

Rod Ellis argues that all interlanguage contains three basic features: “permeability, dynamism, and systematicity” (Davies 461). Interlanguage is permeable because it is “open to external influence from the outside (i.e. through the input). It also open to influence from the inside” (Ellis 33). This permeability allows for evolution of understanding and improved communicative competence as learners receive new input and process it.

Interlanguage is also dynamic in that it is variable. A room full of language learners may all have the same teacher and receive the same lectures and do the same activities, but the way they process the input may result in different outcomes or mental rules.

Finally, as mentioned previously, interlanguage is systematic, the system being shaped by the mental rules the learner has established or invented based on observation, experience, and inference.


Anonymous. “Interlanguage.” Prezi, 17 Feb. 2017,

Davies, Alan. “Is International English an Interlanguage?” TESOL Quarterly, vol. 23, no. 3, 1989, pp. 447–467. JSTOR,

Ellis, Rod. Second Language Acquisition. Oxford, 1997.

“Overview on Interlanguage.” Center for Advanced Research on Language Acquisition, 19 Apr. 2019,