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"Hola" is a form of "hola", an interjection which is often translated as "hello". "Bien, gracias" is a phrase which is often translated as "fine, thank you". Learn more about the difference between "hola" and "bien, gracias" below.
hola
An interjection is a short utterance that expresses emotion, hesitation, or protest (e.g., Wow!).
1. (general)
b. hi  (colloquial)
A word or phrase that is commonly used in conversational speech (e.g., skinny, grandma).
¡Hola! ¿Qué hay de nuevo?Hi! What's new?
bien, gracias( 
byehng
grah
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syahs
)A phrase is a group of words commonly used together (e.g., once upon a time).
1. (general)