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"La camiseta" is a form of "camiseta", a noun which is often translated as "shirt". "Los vaqueros" is a form of "vaquero", a noun which is often translated as "cowboy". Learn more about the difference between "la camiseta" and "los vaqueros" below.
la camiseta(
kah
-
mee
-
seh
-
tah
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
1. (clothing)
c. jersey  (sports) (United States)
Regionalism used in the United States
Los jugadores se intercambiaron las camisetas tras el partido.The players exchanged jerseys after the match.
d. undershirt  (undergarment) (United States)
Regionalism used in the United States
Por favor no salgas a la calle en tu camiseta y calzoncillos.Please don't go outside in your undershirt and boxers.
e. vest  (undergarment) (United Kingdom)
Regionalism used in the United Kingdom
Debes llevar una camiseta debajo de tu camisa.You ought to wear a vest under your shirt.
el vaquero, la vaquera(
bah
-
keh
-
roh
)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).
1. (occupation)
a. cowboy  (masculine)
Mi bisabuelo era un vaquero en el Viejo Oeste.My great-grandfather was a cowboy in the Old West.
¿De qué te vas a vestir para Halloween? - De vaquero.What are you dressing up as for Halloween? - A cowboy.
b. cowgirl  (feminine)
Mi vecina es vaquera en un rodeo en Austin.My neighbor is a cowgirl in a rodeo in Austin.
2. (colloquial) (student who skips class) (Andes)
A word or phrase that is commonly used in conversational speech (e.g., skinny, grandma).
An adjective is a word that describes a noun (e.g., the big dog).
4. (material)
los vaqueros
A plural noun indicates that there is more than one person, place, thing, or idea.
5. (clothing)
a. jeans 
Compramos unos vaqueros Levi's originales en San Francisco, California.We bought some original Levi jeans in San Francisco, California.