This module offers Master’s students an academic overview of how language errors reflect the process of second language learning. It focuses on identifying, classifying, and interpreting learners’ errors to understand their interlanguage development. Grounded in key theories from applied linguistics, the module explores the causes and types of errors and their implications for language teaching and assessment. It aims to help students apply analytical methods to real learner data and use error analysis as a tool for improving pedagogical practices and research in language learning.