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QUICK ANSWER
"What" is a form of "what", a pronoun which is often translated as "qué". "Such a" is a phrase which is often translated as "tal". Learn more about the difference between "such a" and "what" below.
such a()
A phrase is a group of words commonly used together (e.g., once upon a time).
a. tal
You went bowling underwater? I've never heard of such a thing.¿Jugaste al boliche bajo el agua? Nunca he escuchado de tal cosa.
what()
A pronoun is a word that stands in for a noun (e.g., she).
An adjective is a word that describes a noun (e.g., the big dog).
An interjection is a short utterance that expresses emotion, hesitation, or protest (e.g., Wow!).
