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"Estafeta" is a noun which is often translated as "post office", and "batallón" is a noun which is often translated as "battalion". Learn more about the difference between "estafeta" and "batallón" below.
la estafeta(
ehs
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tah
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feh
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tah
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
a. post office 
Para recoger paquetes y cartas en la estafeta hace falta identificarse.You need to show your ID in order to pick up parcels and letters at the post office.
b. sub-post office  (United Kingdom)
Regionalism used in the United Kingdom
Hay una estafeta en la isla desde donde se pueden mandar cartas y paquetes.There's a sub-post office on the island from where letters and packages can be sent.
2. (sport) (Latin America)
Regionalism used in Latin America: all the countries in South America, Central America, and the Caribbean. Does not include Spain.
a. baton 
En las carreras de relevos, hay que pasar la estafeta al siguiente corredor.In relay races, you have to pass the baton to the next runner.
This means that the noun can be masculine or feminine, depending on the gender of the noun it refers to (e.g., el doctor, la doctora).
3. (messenger)
a. courier 
El estafeta entregó una carta dirigida a mi padre.The courier delivered a letter addressed to my father.
el batallón(
bah
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tah
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yohn
)A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).
1. (military)
a. battalion 
Arcadio era un soldado del Quinto Batallón.Arcadio was a soldier of the Fifth Battalion.