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"Vela" is a form of "vela", a noun which is often translated as "candle". "Velo" is a form of "velo", a noun which is often translated as "veil". Learn more about the difference between "vela" and "velo" below.
la vela(
beh
-
lah
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
a. sailing 
El clima está perfecto para hacer vela en la bahía.The weather is perfect to go sailing in the bay.
4. (colloquial) (mucus)
A word or phrase that is commonly used in conversational speech (e.g., skinny, grandma).
a. snot  (colloquial)
A word or phrase that is commonly used in conversational speech (e.g., skinny, grandma).
El pobre bebé tiene la nariz llena de velas.The poor baby has a nose full of snot.
el velo(
beh
-
loh
)A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).
a. veil 
El novio alzó el velo de la novia y la besó.The groom lifted the bride's veil and kissed her.
2. (figurative) (screen)
A phrase used as a figure of speech or a word that is symbolic in meaning; metaphorical (e.g., carrot, bean).
a. veil  (figurative)
A phrase used as a figure of speech or a word that is symbolic in meaning; metaphorical (e.g., carrot, bean).
Al gobierno le conviene tenernos tras el velo de la ignorancia.It is convenient for the government to keep us behind the veil of ignorance.
b. cloak  (figurative)
A phrase used as a figure of speech or a word that is symbolic in meaning; metaphorical (e.g., carrot, bean).
La verdad se esconde detrás de un velo de mentiras.The truth hides behind a cloak of lies.