In linguistics, according to J. Richard et al., (2002), an error is the use of a word, speech act or grammatical items in such a way that it seems imperfect and significant of an incomplete learning (184). It is considered by Norrish (1983, p. 7) as a systematic deviation which happens when a learner has not learnt something, and consistently gets it wrong. However, the attempts made to put the error into context have always gone hand in hand with either [language learning and second-language acquisition] processe, Hendrickson (1987:357) mentioned that errors are ‘signals’ that indicate an actual learning process taking place and that the learner has not yet mastered or shown a well-structured [linguistic competence|competence] in the target language.
All the definitions seeme to stress either on the systematic deviations triggered in the language learning process, or its indications of the actual situation of the language learner themselves, which will later help monitoring, be it an applied linguist or particularly the language teacher to solve the problem, respecting one of the approaches argued in the Error Analysis (Anefnaf 2017). The occurrence of errors doesn't only indicate that the learner has not learned something yet, but also it gives the linguist the idea of whether the teaching method applied was effective or it needs to be changed.
According to Corder (1976), errors signify three things: first to the teacher, in that the learner tells the teacher, if they have undertaken a systematic analysis, how far towards that goal the learner has progressed and, consequently, what remains for them to learn; second, they provide the researcher with evidence of how language is learned or acquired, and what strategies or procedures the learner is employing in their discovery of the language; third, (and in a sense this is their most important aspect) they are indispensable to the learner himself/herself, because the making of errors can be regarded as a device the learner uses in order to learn (p. 167).