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"An" is an indefinite article which is often translated as "un", and "of" is a preposition which is often translated as "de". Learn more about the difference between "an" and "of" below.
an(
ahn
)An indefinite article is a word that indicates that a noun is not specific (e.g., a girl).
1. (general)
A preposition is a word that indicates the relationship between a noun and another word (e.g., He ran through the door.).
of(
uhv
)A preposition is a word that indicates the relationship between a noun and another word (e.g., He ran through the door.).