Grammar 6.4: Five different ways to express obligation

Again, it's totally unnecessary for your textbook to devote a grammar section to this.

All that's being presented here are 5 different ways to express obligation.

• 3 of them are personal (ie, the actant is the one designated as specifically obligated to perform the action);
   
• 2 of them are impersonal (ie, these are generalizations about obligation/s);
   
• All 5 must be followed by a verb in infinitive.

3 verbs/verb phrases for personalized expressions of obligation (ie, the actant is the one designated as specifically obligated to perform the action):

• Tener que: to have to
• Deber: to should
• Necesitar: to need to
• Deber and necesitar are completely regular verbs, and neither one stem changes. You already know how to conjugate tener.
• You choose the verb to use based on what you intend to convey.
   
• Remember: all 3 must be followed by a verb in infinitive.
• Necesito estudiar para el examen final.
• Debes hacer ejercicio todos los días.
• La profesora tiene que leer nuestras composiciones.

2 verb phrases for impersonal expressions of obligation (ie, generalizations about being obligated to perform an action):

• Es necesario: It's necessary
• Hay que: One must
   
• You choose the phrase to use based on what you intend to convey.
• Remember: "Es" and "hay" always stay "es" and "hay" in these expressions. Don't change them.
   
• Both phrases must be followed by a verb in infinitive.
• Es necesario estudiar para el examen final.
• Hay que hacer ejercicio todos los días.