Obligation, necessity, prohibition, and advicemust, have to, need to, should, and their negatives.Related learning areasEnglish GrammarRelated conceptsAdjectives — order, gradability, and comparisonAdverbs — form and positionbe, do, and have as auxiliary and main verbscan, could, and be able toFirst and second conditionalsFuture forms — will and be going toQuestionsAll questions in this subjectStart learningStart free practice