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"Atrasar" is a transitive verb which is often translated as "to postpone", and "retrasar" is a transitive verb which is also often translated as "to postpone". Learn more about the difference between "atrasar" and "retrasar" below.
atrasar(
ah
-
trah
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sahr
)A transitive verb is a verb that requires a direct object (e.g., I bought a book.).
a. to postpone 
Los novios atrasaron su boda por cuestiones de salud.The bride and groom postponed their wedding for health reasons.
b. to delay 
Tendremos que atrasar la construcción hasta conseguir los permisos.We'll have to delay construction until we get the permits.
c. to put back 
Tuvimos que atrasar la fiesta de compromiso porque mi padre sufrió un infarto.We had to put back the engagement party because my father had a heart attack.
a. to delay 
La oposición de los vecinos atrasó la construcción de la gasolineraOpposition from neighbours delayed construction of the gas station.
3. (clocks)
a. to put back 
El domingo tenemos que atrasar nuestros relojes una hora.We need to put our clocks back by an hour on Sunday.
An intransitive verb is one that does not require a direct object (e.g., The man sneezed.).
4. (clocks)
a. to be slow 
El reloj de la cocina atrasa; tendremos que cambiarle la pila.The kitchen clock's slow; we'll need to change the batteries.
b. to lose time 
Mi reloj atrasó sin que me diera cuenta y llegué tarde a la cita.My watch was losing time without my realizing it, so I was late for the appointment.
c. to lose 
Este reloj atrasa venticinco segundos al dÃa.This clock loses twenty-five seconds a day.
d. to run slow 
Tu despertador atrasa. No son las 5:15, son las 5:20.Your alarm clock runs slow. It's not 5:15, it's 5:20.
atrasarse
A pronominal verb always uses a reflexive pronoun. (e.g., Te ves cansado.).
a. to fall behind 
Susana se atrasó en sus estudios y no ha terminado la carrera.Susana fell behind with her studies so she hasn't finished her degree.
b. to get behind 
Los inquilinos se atrasaron en el pago de la renta el mes pasado.The tenants got behind with their rent last month.
a. to be late 
El camión se atrasó tanto que nos tuvimos que ir en taxi.The bus was so late that we had to take a taxi instead.
b. to be delayed 
Emilia se atrasó porque se le ponchó una llanta.Emilia was delayed because she had a flat tire.
c. to get held up 
Me atrasé en el trabajo y perdà el tren.I got held up at work and missed my train.
7. (clocks)
a. to be slow 
Llegué tarde al examen porque mi reloj se atrasó.I was late for the exam because my watch was slow.
b. to lose time 
Este reloj se atrasa a pesar de que le cambié la pila la semana pasada.This clock is losing time despite my changing the battery last week.
a. to be late 
A MarÃa se le atrasó la menstruación y resultó que estaba embarazada.MarÃa's period was late, and it turned out she was pregnant.
b.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
Supongo que es normal atrasarse durante la perimenopausia.I guess it's normal to have late periods during the perimenopause.
Muchas veces me atraso; no quiere decir que esté embarazada.My period's often late; it doesn't mean I'm pregnant.
retrasar(
rreh
-
trah
-
sahr
)A transitive verb is a verb that requires a direct object (e.g., I bought a book.).
1. (to defer)
a. to postpone 
Retrasamos la reunión porque dos miembros del comité estaban enfermos.We postponed the meeting because two members of the committee were sick.
b. to delay 
El autor retrasó la publicación de su autobiografÃa varios años.The author delayed the publication of his autobiography for many years.
a. to put off 
Retrasé la redacción hasta la última hora porque tenÃa ganas de pasar el dÃa viendo el maratón de Star Trek.I put off my essay to the last minute because I wanted to spend the day watching the Star Trek marathon.
a. to set back  (United States)
Regionalism used in the United States
¿Retrasaste tu reloj? Ya no estamos en horario de verano.Did you set your watch back? It's not Daylight saving time anymore.
b. to put back  (United Kingdom)
Regionalism used in the United Kingdom
Ese reloj está adelantado. Tienes que retrasarlo 25 minutos.That clock is fast. You need to put it back 25 minutes.
An intransitive verb is one that does not require a direct object (e.g., The man sneezed.).
5. (of a clock)
a. to be slow 
No consultes ese reloj. Retrasa 20 minutos.Don't look at that clock. It's 20 minutes slow.
retrasarse
A pronominal verb always uses a reflexive pronoun. (e.g., Te ves cansado.).
a. to be running late 
Perdà mi vuelo porque me retrasé 15 minutos.I missed my flight because I was running 15 minutes late.
a. to be delayed 
Llegamos tarde porque el tren se retrasó.We arrived late because the train was delayed.
b. to be held up 
La misión se retrasó un mes debido al clima desfavorable.The mission was held up for a month due to bad weather.
a. to fall behind 
El propietario me quiere echar porque me retrasé con la renta.The landlord wants to kick me out because I fell behind with the rent.
9. (of a clock)
a. to be slow 
El reloj en mi carro siempre se retrasa 15 minutos.The clock in my car is always fifteen minutes slow.
10. (in studies)
a. to fall behind 
Me retrasé en la facultad porque tuve que empezar a trabajar para pagar la renta.I fell behind in school because I had to start working to pay the rent.