The four main language skills that are assessed are reading, writing, listening, and speaking. These skills should be integrated during assessment rather than tested individually to allow for a more authentic assessment of language ability. Grammar, vocabulary and phonology are not valid assessments when isolated and must be assessed through skills. There are two factors to consider in integrated skills assessment: performance, how a student carries out a task, and competence, their ability to achieve the goal of the task using integrated skills. Sometimes performance does not demonstrate true competence if factors like illness affect performance. Multiple measures provide a more reliable assessment than a single measure.