Permitir vs. dejar
Both permitir and dejar can mean to let or to allow, but they are used in different contexts and with different nuances in Spanish.
Permitir
B1The word permitir means to permit or to allow. This verb is more formal and is often used in contexts where rules, regulations, or official permissions are involved.
El jefe permitió que tomáramos un descanso.
(The boss allowed us to take a break.)
No se permite fumar en el edificio.
(Smoking is not allowed in the building.)
Sus padres no le permiten salir hasta tarde.
(Her parents don't allow her to stay out late.)
El sistema no permite acceso sin contraseña.
(The system does not allow access without a password.)
Dejar
A2Dejar can also mean to let or to allow, but it is less formal and more commonly used in everyday conversation. It can also mean to leave or to stop doing something, adding to its versatility.
Déjame ayudarte con eso.
(Let me help you with that.)
Mi madre no me deja volver tarde a casa.
(My mother doesn't let me come home late.)
Voy a dejar mi trabajo a fin de mes.
(I'm going to leave my job at the end of the month.)
Dejó de fumar hace años.
(He stopped smoking years ago.)
Summary
Permitir is more formal and often used in official or regulated contexts, while dejar is less formal and more common in everyday speech. Additionally, dejar has other meanings like to leave or to stop doing something, making it a more versatile word.