"Fossilization" is the condition in which a learner’s interlanguage has stabilized while still unfinished. Forms that remain inaccurate or absent in the learner’s production despite adequate exposure and instruction are referred to as "fossilized forms". This concept is quite scary for language learners and is similarly alarming to language teachers. This phenomenon must be put it into perspective however. In order to truly understand fossilization, there are a few things that one must also know.

a)  It is normal and often acceptable for adult ESL learners to become fossilized.

b)  Fossilization doesn't interfere with a learner’s daily communication needs.

c)  Fossilization doesn’t affect children or EFL learners.

d)  Fossilization depends largely on the learner and her desire to progress.

It is quite normal and

Firstly, in order to understand fossilization, one must also know that fossilization seems to be the normal end for adult learners. Research shows that few adult language learners, if any, totally "master" the target language. Generally, their interlanguages stabilize (i.e. they finish learning) while still not having mastered the target language’s pronunciation or grammar. Most immigrants who come to the United States after puberty for example, retain their foreign accent, and a variety of errors generally related to interlingual transfer. This needn’t be viewed as a terrible condition however. There is no reason why every language learner should be required to master native-like pronunciation, and, many learners might never need to use certain forms perfectly in order to function in their daily lives. In some sense, they could be seen as retaining some of their cultural identity, and, they have a right to do so. In some cases, they might even be benefiting from having some exotic and flavorful mannerisms.

Secondly, it is important to point out that fossilization’s effects are very limited. Fossilization does not affect all components of proficiency, but instead, seems to be very selective, only affecting certain areas such as pronunciation, syntax, and morphology, and even then only affecting specific forms. In particular, fossilization does not affect fluency. In fact, it will not happen unless the learner is already quite fluent. It also does not seem to affect the growth of the learner’s vocabulary, although it may manifest itself as incorrect vocabulary usage (e.g. *"Two children make me difficult."). The most common kind of fossilization is the learner’s inability to master native-like pronunciation. Nearly all adult learners continue to keep their accent no matter how long they use the target language. This situation is clearly seen in those who immigrate to the United States after puberty. Some syntactic errors can also remain after many years. One example of this would be long lasting difficulty with the placement of adverbs in English. Some learners might continue to make sentences such as *"I visit frequently this place" even after 50 years or more in the United States. In other cases learners might not develop the proper use of certain relative clause forms and instead continue to use some communicative strategy such as simply stringing two sentences together. For example, they might say, *"I saw the man he stole your car" instead of "I saw the man WHO stole your car." They might use one referent for all forms as in the case of "I saw the man WHAT stole your car". Every American has at some point spoke with a Chinese American who never learned plurals (e.g. "How many apple you want?").

What all these errors have in common however is that they generally don’t interfere in communication, won’t be corrected by the listener, and won’t cause the speaker any embarrassment. In other words, fossilization never seriously interferes with the language learner’s routine communicative needs. It also seems that, if the learner’s routine communicative needs changed and then required her to use those forms correctly, she could. If a fossilized learner needs to learn how to speak correctly in order to better herself somehow (e.g. employment or education), then she can learn how to use those forms correctly and do so - at least while in the contexts in which it is necessary (i.e. she might continue to use the fossilized forms in contexts where she does not need to speak correctly). For example, a fossilized language learner who works as a doctor, might use the correct form when writing for a medical journal and then use the fossilized forms with her children at home. This ability to unlearn these supposedly "permanent" incorrect forms suggests that fossilization depends greatly on the learner’s personality and environment. Since fossilized forms can be corrected if they become necessary to the learner, we can assume that fossilization is not actually permanent at all.

The third major point to keep in mind is that fossilization does not seem to occur in children, and generally only occurs in certain ESL situations (e.g. immigrants). Children, with their special innate ability and their ability to adapt to new cultures, seem to be naturally guided to find the correct forms. Adults on the other hand, may be lacking various types of flexibility necessary to completely master a second language: this flexibility could be neurological, neuromuscular, or just psychological. EFL learners are also unlikely to fossilize simply because they will probably never get enough opportunities to use the language to the point which it becomes so deeply internalized. EFL learners can get stuck, and of course they can use incorrect forms, but this is not fossilization – those problems are just par for the course. Fossilization is most likely to happen in cases in which the learner does not seem to need or even care for mastery. It may happen to a housewife who figures that she can do just fine without subject-verb agreement and is too tired to care. It may happen to a taxi driver who doesn’t say much more than "Where do you need to go?" all day, and speaks only his first language in his home neighborhood. It may even happen to a university professor who needs to express very precise ideas but doesn’t mind expressing them with a rich and exotic accent that somehow makes him more special. In nearly all cases, it involves language learners who don’t feel the need to totally assimilate into the target culture and would rather maintain their own cultural identity. They might even live in a neighborhood of immigrants from their homeland (e.g. Korea Town or Little Italy).

The final point that must be taken into account is that, fossilization, although said to take place through the same processes as regular language acquisition, differs in a number of ways. Just as regular language forms get internalized over an extended period of time through frequent communicative use, so too do fossilized forms. When a form is frequently used to communicate, it gets internalized, begins to automatize and eventually comes out of the learner fluently and effortlessly. So too may incorrect forms become internalized and come out of the learner automatically. This has led some researchers to worry that language teaching without any focus on form or error correction can lead to the internalization of incorrect forms - fossilization. No language teacher wants to be responsible for allowing an incorrect form to become internalized into a learner. For this reason, communicative language teaching began to include more form-focused instruction and error correction (note: "focus on form" does not include decontextualized, explicit grammar instruction). Normal language acquisition however, does not necessarily involve forms getting used frequently and then becoming irreversible (i.e. "habit formation") as in the case of fossilization. All language learners go through stages in which they will use an incorrect form for an extended period of time before eventually being ready to learn the correct form. The continued use of those incorrect forms does not usually lead to permanent incorrect forms. Normal language learning involves stages like this, so why do certain forms never move into a correct stage despite years of exposure to input and instruction?