Obligation and responsibility: must and have to
The pattern
Must and have to are modal verbs of obligation and responsibility. Must never changes form and is followed by the base verb: "I must study." Have to behaves like a normal verb: it takes do/does/did and the person changes it: "She has to work", "They had to leave." Affirmative obligation is where they are close. The big difference shows in the negative: must not (mustn't) means it is forbidden; do not have to (don't have to) means there is no obligation, you can choose.
| Forma | Significado | Ejemplo |
|---|---|---|
| must + verbo | obligación que asumo yo | I must finish my homework. |
| have to + verbo | obligación de una regla externa | We have to wear a uniform. |
| must not / mustn't | prohibición | You mustn't cheat. |
| don't have to | no hay obligación (puedes elegir) | You don't have to come early. |
Worked example, step by step: a to-do list
Task: write the responsibilities of a school event. Step 1: pick duties. Step 2: decide the source of each. A rule from the school uses have to: "Everyone has to arrive at 8 a.m." A promise you make to yourself uses must: "I must check the microphone." Step 3: add a prohibition with must not: "We must not forget the guests." Step 4: add something optional with don't have to: "You don't have to bring food." The finished list shows obligation, prohibition and free choice clearly.
Practice
Ejemplo resuelto — Which sentence shows an obligation that comes from an outside rule?
El planteamiento
Which sentence shows an obligation that comes from an outside rule?Razonamiento
A uniform is imposed by the school, so it uses have to.Respuesta correcta
Students have to wear a uniform.
Paso 1 de 3
Which sentence shows an obligation that comes from an outside rule?
"You ___ park here; it is a no-parking zone."
"You don't have to wear a tie" means wearing a tie is forbidden.
Completa: para una obligación que impone una regla uso ; para una prohibición uso ; para decir que algo NO es obligatorio uso .
Escribe tu lista de tareas de hoy en inglés: dos obligaciones externas con have to, un compromiso personal con must, una prohibición con must not y algo opcional con don't have to.
Se revisa que uses have to para reglas externas, must para un deber propio y que no mezcles must not con don't have to.
Tu texto se guarda sólo en este dispositivo.
Domain check
Can you express obligation, prohibition and free choice?
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