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"Behind" is a preposition which is often translated as "detrás de", and "on" is a preposition which is often translated as "en". Learn more about the difference between "behind" and "on" below.
behind(
bi
-
haynd
)A preposition is a word that indicates the relationship between a noun and another word (e.g., He ran through the door.).
a. detrás de 
The kids hid behind the curtains to surprise the birthday girl.Los niños se escondieron detrás de las cortinas para sorprender a la cumpleañera.
c. tras 
There was a little mouse behind the wardrobe, and when we moved it, it ran away.Había un ratoncito tras el armario y, cuando lo movimos, salió corriendo.
a. detrás de 
Alexa is slightly behind Tracy in the overall season scores.Alexa está ligeramente detrás de Tracy en la puntuación global de la temporada.
b. atrás de 
Gonzalez was behind Uribe in the polls, but he's catching up.González iba atrás de Uribe en las encuestas, pero lo está alcanzando.
c. a la zaga 
Our team is behind all the rest this season.Nuestro equipo está a la zaga de los demás esta temporada.
d. tras 
We're not behind them in the league table, we're ahead of them.Nosotros no vamos tras ellos en la clasificación de la liga, estamos por delante de ellos.
a. por detrás de 
Seattle is three hours behind New York.Seattle está tres horas por detrás de Nueva York.
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
I thought you were going to be behind my idea of hiring Carlos on an interim basis.Pensé que iban a respaldar mi idea de contratar a Carlos como empleado interino.
Why aren't you behind me on this proposal?¿Por qué no me apoyas con esta propuesta?
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
Anne has 25 years of teaching behind her.Anne tiene 25 años dando clases en su haber.
We have a lot of experience behind us.Tenemos mucha experiencia en nuestro haber.
An adverb is a word that describes a verb, an adjective, or other adverbs (e.g., to run quickly, very tired).
c. de cerca 
Cecilia was nervous because the same black van had been following close behind for ten minutes.Cecilia estaba nerviosa porque la misma camioneta negra la había estado siguiendo de cerca por diez minutos.
a. más atrás 
Remember that Mexico City is 2 hours behind.Acuérdate que la Ciudad de México va dos horas más atrás.
A noun is a word referring to a person, animal, place, thing, feeling, or idea (e.g., man, dog, house).
10. (buttocks)
a. el trasero (M)
(m) means that a noun is masculine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
She slapped him on the behind.Le dio una palmada en el trasero.
on(
an
)A preposition is a word that indicates the relationship between a noun and another word (e.g., He ran through the door.).
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
Our anniversary is on Saturday.Nuestro aniversario es el sábado.
Where were you on the morning of September 30th?¿Dónde estabas la mañana del 30 de septiembre?
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
Are you on any medication?¿Toma algún medicamento?
The driver was a young kid on drugs.El conductor era un chico que iba drogado.
a. de  (trip, tour or vacation)
The band will be on tour until December.El grupo estará de gira hasta diciembre.
a. en  (the Internet)
I spent hours on the Internet looking for information for my paper.Pasé horas en Internet buscando de información para mi trabajo.
b. a  (the phone)
I have to talk with my boss, but he's on the phone at the moment.Tengo que hablar con mi jefe pero está al teléfono ahora mismo.
11. (radio or TV)
12. (transport)
b. a  (into a bus, train or airplane)
We got on the plane at six, but we only took off half an hour later.Subimos al avión a las seis pero tardamos media hora en despegar.
13. (music)
a. a 
Playing on keyboards, Dave! A big round of applause for him!¡Al teclado, Dave! ¡Un fuerte aplauso para él!
14. (according to)
a. según 
The order will be delivered based on your instructions.Se entregará el pedido según sus instrucciones.
a. por cuenta de 
The dinner is on my father, and I will buy the cinema tickets.La cena va por cuenta de mi padre y yo pago las entradas para el cine.
An adverb is a word that describes a verb, an adjective, or other adverbs (e.g., to run quickly, very tired).
17. (in place)
18. (with clothing)
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
From next year on, I will be pursuing my real dream.A partir del año que viene, perseguiré mi verdadero sueño.
There's a gas station a couple of miles further on.Hay una gasolinera un par de millas más adelante.
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
Dream on; nothing is impossible!¡Sigue soñando, que nada es imposible!
She went on and on about how smart her kids were.No paraba de hablar de lo inteligentes que eran sus hijos.
An adjective is a word that describes a noun (e.g., the big dog).
21. (in operation)
a. encendido 
If the lights are on, the store's open.Si las luces están encendidas, la tienda está abierta.
b. prendido  (Latin America)
Regionalism used in Latin America: all the countries in South America, Central America, and the Caribbean. Does not include Spain.
While the oven is on, I'll bake this cake.Como está prendido el horno, hornearé esta torta.
22. (occurring)
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
The race is on to find the missing ship.Ya empezó la carrera para encontrar el barco desaparecido.
This event is still on, despite the rain!¡El evento sigue en pie a pesar de la lluvia!
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
Is there anything good on at the movies?¿Están dando algo bueno en el cine?
Your favorite song is on right now.Está sonando tu canción favorita ahora mismo.
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
I bet you $20 she doesn’t turn up. - You’re on!Te apuesto $10 a que no viene. - ¡Trato hecho!
I'll buy you dinner if you ask her out. - OK, you're on.Te invito a cenar si le pides que salga contigo - Vale.