This document discusses principles of language assessment. It defines key terms like assessment, tests, measurement, evaluation, formative assessment, and summative assessment. It also describes different types of tests like achievement tests, diagnostic tests, placement tests, proficiency tests, and aptitude tests. The document outlines principles of language assessment including practicality, reliability, validity, authenticity, and washback effect. It provides examples to illustrate each principle and explains how they help ensure quality in language assessment.