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"Best known" is an adjective which is often translated as "más conocido", and "noun" is a noun which is often translated as "el sustantivo". Learn more about the difference between "best known" and "noun" below.
best known( 
behst
non
)An adjective is a word that describes a noun (e.g., the big dog).
1. (general)
a. más conocido 
Bach was the best-known musician of his time.Bach fue el músico más conocido de su época.
b. mejor conocido 
Leonardo da Vinci had many interests, but was best known for his art.Leonardo da Vinci tenía muchos intereses, pero fue mejor conocido por su arte.
noun(
naun
)A noun is a word referring to a person, animal, place, thing, feeling, or idea (e.g., man, dog, house).
1. (grammar)
a. el sustantivo (M)
(m) means that a noun is masculine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
The noun must agree with the verb in number.El sustantivo debe concordar con el verbo en número.