Errors may occur in the speech or writing of a second or foreign language. An error is the use of a linguistic item in a way which, from the viewpoint of a native speaker, is regarded as faulty,or as the result of incompetent learning. Errors have been classified into various types. When an error results from incomplete knowledge it is called an error.When it is made by a learner due to fatigue, carelessness, or lack of attention, it is called a mistake. When an error belongs to vocabulary it is called a lexical error,when it is in pronunciation it is called a phonological error, and when it occours due to lack grammatical knowledge, it is a syntactic error.When an error is due to the misunderstanding of a speakers intention or meaning it is called an interpretive error,and when its is due to the production of wrong communicative effect, it is a programmatic error.Sometimes an error occurs in the use of a major element of sentence structure. That makes it difficult or impossible to understand. Such an error is called a global error. An error in the use of a first or second language learner may be the result of a normal pattern of development. Such an error is called a developmental error. So error of a language learner may be of different classes.
Everyone is subjected to commit errors and mistakes, may they be a native speaker or not. Personally, someone cannot totally omit such things, especially when learning a language or two. Indeed, as time passes by, changes in how a language was spoken and used can happen over time. With this, language learners are responsible to adapt but upon the process of learning, we are still vulnerable to have such mistakes.