QUICK ANSWER
"Drop in" is an intransitive verb phrase which is often translated as "pasar", and "drop off" is a transitive verb phrase which is often translated as "dejar". Learn more about the difference between "drop in" and "drop off" below.
drop in(
drap
ihn
)An intransitive verb phrase is a phrase that combines a verb with a preposition or other particle and does not require a direct object (e.g., Everybody please stand up.).
1. (colloquial) (general)
A word or phrase that is commonly used in conversational speech (e.g., skinny, grandma).
a. pasar
If we have time, we'll drop in after lunch.Si tenemos tiempo, pasaremos después del almuerzo.
b. dejarse caer (colloquial)
A word or phrase that is commonly used in conversational speech (e.g., skinny, grandma).
Since they were in the neighborhood, they thought they would drop in on Marc and Guille.Como estaban en el barrio, se dejaron caer en casa de Marc y Guille.
drop off(
drap
af
)A transitive verb phrase is a phrase that combines a verb with a preposition or other particle and requires a direct object (e.g., take out the trash.).
An intransitive verb phrase is a phrase that combines a verb with a preposition or other particle and does not require a direct object (e.g., Everybody please stand up.).
a. disminuir
The store was doing really well, and then sales started to drop off when the recession hit.Nos estaba yendo muy bien en la tienda, y luego las ventas empezaron a disminuir cuando llegó la crisis.
a. caerse
I heard a clank and something drop off, so I stopped the truck to check it out.Oí un sonido metálico y algo que se cayó, así que paré la camioneta para revisar.
4. (colloquial) (to fall asleep)
A word or phrase that is commonly used in conversational speech (e.g., skinny, grandma).
a. dormirse
She dropped off around nine o'clock, but then woke up again at midnight with a start.Se durmió a eso de las nueve, pero volvió a levantarse sobresaltada a las doce.
b. quedarse dormido
I must have dropped off because I woke up, and all the money was gone.Me he de haber quedado dormido porque cuando me desperté, todo el dinero había desaparecido.
