This document discusses error analysis in second language learning. It begins by defining error analysis and distinguishing between errors and mistakes. Four main models of error analysis are described: Corder's 3 stage model, Ellis' elaboration, Gass and Selinker's 6 step model, and Richards' classification of error sources. Errors can be classified linguistically or by the process involved. The significance of errors for learners, teachers and researchers is explained. Pedagogical implications include using findings to prevent errors and provide feedback and correction.