The term “interlanguage” was coined by American linguist, Larry Selinker, in recognition of the fact that L2 learners construct a linguistic system that draws , in part, on the learner’s L1 but is also different from it and also from the target language. A learner’s interlanguage is, therefore, a unique linguistic system. The concept of interlanguage involves the following premises about L2 acquisition:

1. The learners construct a system of abstract linguistic rules which underlies comprehension and production of L2. This system of rules is viewed as “mental grammar” and is referred to as “interlanguage”.

2. The learner’s grammar is permeable. That is, the grammar is open to influence from the outside ( i.e. through the input). It is also influenced from the inside. For example, the omission, overgeneralization, and transfer errors which constitute in evidence of internal processing.

3. The learner’s grammar is transitional. Learners change their grammar from one time to another by adding rules, deleting rules, and restructuring the whole system. This results in an interlanguage continuum. That is, learners construct a series of mental grammars or interlanguages as they gradually increase the complexity of their L2 knowledge.

4. Learners employ various learning strategies to develop their interlanguages. The different kinds of errors learners produce reflect different learning strategies. For example, omission suggests that the learners are in some way simplifying the learning task by ignoring grammatical features that they are not ready to process.

5. The learner’s grammar is likely to fossilize. Selinker suggested that only about five percent of learners go on to develop the same mental grammar as native speakers. The majority stop some way short. The prevalence of backsliding (production of errors representing an early stage in development) is typical of fossilized learners. That way the same errors tend to be repeated by the same individuals, even though that does not mean the interlanguage has stopped its continuum.

“That is” (L 11) introduces a/an: