The difference between an error and a mistake in terms of language use

Although most dictionaries present these words as synonyms, there is a sharp difference between them as regards language use.

An error is a frequent and systematic violation of the rules of language at all levels of language study: phonology, semantics, syntax, morphology. It also refers to the use of language forms in an inappropriate context. Therefore, knowing the rules of a language is not enough because we also need to use these language forms in the appropriate context.

A mistake, on the other hand, refers to a mere lapse or slip which is not part of the linguistic repertoire or knowledge of the speaker and can be corrected by the speaker himself.

An error, for example, is when you always write “I thought him how to read and write.” or  say “I belongs to everyone.” without knowing that the “thought” and “belong” in these sentences are supposed to be “taught” and “belong” respectively. As regards error, the speaker is unable to correct himself/herself even when his/her attention is drawn to the lapses. The speaker can even repeat the same slip in different occasions if need be. Therefore, an error is habitual and recurrent. The speaker does not know that he or she has violated the language rules because it is not part of his or her knowledge base. 

On the contrary, if a speaker makes a statement like either of the ones above but immediately corrects himself on realizing that he has committed a slip, it becomes a mistake. A mistake can be committed as a result of loss of memory, tension, sickness, tiredness etc.

 From the foregoing, we can say that mistakes are accidental whereas errors are made due to lack of knowledge.