Obligation, necessity and permission (must, have to, can)

💡 Don't have to means that buying a ticket is not necessary.

💡 Questions normally use do/does + have to.

💡 Mustn't or must not + bare infinitive says an action is prohibited.

💡 Must can express a strong feeling or wish of the speaker.

💡 Must marks obligation, don't have to marks no necessity, can marks permission, and can't marks prohibition.

💡 A question about obligation uses do + subject + have to + bare infinitive.

💡 Mustn't + bare infinitive expresses a strong prohibition.

💡 Can + subject + bare infinitive is used to ask for permission.

💡 Don't have to expresses lack of necessity, not prohibition.

💡 Has to reports an external rule for the singular subject every employee.

💡 Have to is a natural choice for an obligation imposed by an outside rule.

💡 Short replies repeat can for permission questions and do/does for have to questions.

💡 Can't or cannot expresses that the action is not permitted.

💡 Modal must is followed directly by the base form without to.

💡 Don't have to means there is no obligation.

💡 The question form is Do + subject + have to + bare infinitive?

💡 Don't have to indicates that bringing shampoo is unnecessary.

💡 Written instructions often use must + bare infinitive.

💡 Modal verbs do not take a third-person -s ending.

💡 Can + bare infinitive gives permission.