Brief Overview

This is a brief overview of interlanguage for the reader to understand the main points. Readers are encouraged to study more in-depth to gain a full appreciation of the history, development, and implementation of this theory as it contains an extreme amount of complex information. How far down the rabbit hole do you want to go? At the end are guiding questions for the educator to contemplate instruction and Interlangauge.

Interlanguage is a term that describes the language learner’s journey from his native language (L1) to acquisition of the target language (L2). Larry Selinker, who is credited with first proposing the interlanguage theory, was inspired by Corder’s error analysis which attempted to examine and classify the errors of language learners. Interlanguage theory tried to determine if there was a continuum in the internal grammar of learning additional languages, and through research, resolve if learners acquired L2 in much of the same fashion as L1.  Ultimately, there would be similarities, but not the same.

Interlanguage viewed language development as a combination of several factors including nature of input, environment, internal processing of the learner, and influence between L1 and L2. Thus began an explosion of research into understanding how language and the internal grammar in second language learners evolved.

There has been a wide range of research investigating interlanguage with various levels, ages, and languages. The results have led to understanding interlanguage as embodying the characteristics of being systematic, dynamic, and variable.

  • Systematic: the learner forms an internal construct of grammatical rules and structures. These grammatical rules may or may not mirror the proper rules of the L2 being learned. Educators can extrapolate what rules the learner has formed through analyzing errors and the correct usage of the language. In other words, the language learner doesn’t use language haphazardly, but uses a system of internal rules that can differ from the target language.
  • Dynamic: Although the internal rules are systematic, the rules are not static and have the ability to be altered through various means.
  • Variable: The context may determine the language and rules the learner acquires. There are numerous factors involved with language and rule acquisition that vary from person to person, such as the nature of input (instruction, TV, etc..),  the environment (classroom, etc..), and exposure (foreign language, second language, etc…) to language.

An analogy that compares to this is a person from earth moves to live on the moon (an English speaking student studying Korean). As the person is standing on earth, he is totally an earthling (at first, the student will only view Korean in terms of the English language), but as he climbs in the spaceship and takes off (as he begins to learn Korean), his distance from the earth increases so he is not totally an earthling anymore (the person starts adopting Korean language rules, structures, culture). As the person breaks through the outer atmosphere of earth, he is still closer to earth, but he is moving towards the moon to become an alien (he understands more of what it means to use Korean and to think like a Korean). In between the earth’s atmosphere and landing on the moon (native Korean), the person will reside in the vast emptiness of space. The person is in between the two celestial bodies, but not a part of either one. This is interlanguage- the language is between two, but can’t be classified as either one.

For this reason, interlanguage is thought of as a third language that is unique to the individual learner. The learner is in a limbo state as far as language is concerned because it neither mirrors the L1 or L2.

Along with interlanguage comes a very controversial topic called fossilization. With language learning, people do not ascend to higher levels as if it is a staircase that goes from the bottom floor (beginner) to an extremely high second floor (native speaker). Instead of a constant step up, language learners follow spurts of growth followed by plateaus of knowledge. One way to think of this is to say that the Empire State Building has two stairways- stairway A on the east side of the building and stairway B on the west side of the building. Instead of being able to take stairway A from the ground floor to the very top, the person takes stairway A up to the second floor, enters the hall, and goes to the opposite end of the building to stairway B. At stairway B, the person goes to the 3rd floor, enters the hallway, and goes to the opposite end of the building to stairway A. This repeats over and over with the person alternating stairways and floors until the person reaches the top of the building (native fluency).

Now fossilization is when a person is making their way from bottom to top and somewhere during the process they become stuck on one floor. So in our illustration of the Empire State Building, if the person achieves the 70th floor, but fossilizes, then it’s not possible for him to make it to the 71st floor. The 70th floor is a pretty high level, but it’s not native like in fluency. Likewise, if a person becomes fossilized on the 5th floor, then it is not possible for him to reach the 6th floor. This level is really low so his ability to communicate in that language would be almost non-existent.


Interlanguage has multiple dimensions that make it impossible to list in an article like this, but interlanguage carries a lot of research to show the validity of the hypothesis. The biggest controversy comes from the fossilization aspect that explains why learners fail to reach various levels. Some educators tend to disregard the fossilization aspect of interlanguage, but others tend to recognize that some learners do reach states where learning ceases so fossilization is possible.

How Not To Use

  • Systematic but not according to the system: The learner’s language and internal grammar is not haphazard, but is a system that is understood by the learner. Some educators instruct students by telling grammar rules and expect the learner to fully understand it because “I told the exact rule.” Language leaves a lot of room for interpretation and the learner’s internal grammar most often will not mirror that of the actual rule at first. Students need time to understand, internally work the information into what they already know, and then have chances to test their hypotheses according to how they have internalized it. Just because the rule has been told or written on the board, doesn’t mean the students will understand it.

Find out more information on how to not to use interlanguage in our online SLA course. Get information and discounts on our course HERE.

How To Apply

  • Dynamic is dynamite! The systematic rules the students have formulated are dynamic and can be altered or transformed. This is good news as there is not so much pressure to get it right the first time. The educator can review previous material in following lessons to help assist the students with internalizing the rule properly. Also it should provide hope for the educator, even though the students do not currently understand it properly, with more input and strategic implementation the learners can alter their misunderstandings.

Find out more information on how to use interlanguage in our online SLA course. Get information and discounts on our course HERE.

Final Thoughts

Interlanguage is a great theory to keep educators grounded as to what goes on in the learning process. Educators have tendencies to believe students are huge buckets we just pour information into and they learn it. The learners may be huge buckets, but those buckets have thick filters that trap a lot of the information that is trying to be passed along. As educators, we must understand that the learner’s rules don’t follow what is taught, but they are dynamic and changeable. Also, regardless if you believe fossilization exists, the educator should always assess where the students are not acquiring knowledge appropriately and devise better strategies and plans on teaching.

Also, interlanguage is great to use when threading together a lesson plan. The realization that students will interpret information differently should provide some guidance on how instruction of the information should be presented. The first segment of the lesson plan should allow for a portion of the information to be learned, and then the following segments should review and build upon that learning.