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"Hola" is a form of "hola", an interjection which is often translated as "hello". "Precioso" is an adjective which is often translated as "beautiful". Learn more about the difference between "hola" and "precioso" 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?
precioso(
preh
-
syoh
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soh
)An adjective is a word that describes a noun (e.g., the big dog).
1. (pretty)
a. beautiful 
La vista desde la peña está preciosa.The view from the cliff is beautiful.
Este es un broche precioso. ¿Dónde lo compraste?This is a beautiful brooch. Where did you buy it?
b. gorgeous 
Estás preciosa con tu nuevo vestido y tu nuevo corte de pelo.You look gorgeous with your new dress and your new haircut.
c. lovely 
Es un día precioso. ¿Por qué no damos un paseo en el parque?It's a lovely day. Why don't we go for a walk in the park?
2. (of value)
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).
b. sweetheart 
No te preocupes, preciosa. Todo saldrá bien, ya verás.Don't worry, sweetheart. Everything will be ok, you'll see.