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"No sé" is a phrase which is often translated as "I don't know", and "¡Bah!" is an interjection which is often translated as "Bah!". Learn more about the difference between "no sé" and "¡Bah!" below.
no sé(
noh
 
seh
)
A phrase is a group of words commonly used together (e.g., once upon a time).
phrase
a. I don't know
No sé si quiero pizza o un sándwich.I don't know if I want pizza or a sandwich.
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¡Bah!(
bah
)
An interjection is a short utterance that expresses emotion, hesitation, or protest (e.g., Wow!).
interjection
a. Bah!
¡Bah! ¡No sé! Mejor preguntémosle.Bah! I don't know. We'd better ask her.
b. Huh!
¡Bah! ¡Qué raro!Huh! That's strange!
c. Oh well!
¡Bah! Si no le interesa venir, ¿qué le vamos a hacer?Oh, well! If she's not interested in coming, what can we do?
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