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"In addition" is a phrase which is often translated as "además", and "besides" is a preposition which is often translated as "además de". Learn more about the difference between "in addition" and "besides" below.
in addition()
A phrase is a group of words commonly used together (e.g., once upon a time).
1. (adverbial)
a. además
In addition, the school will offer food and beverage on the field trip.La escuela ofrecerá además comida y bebida en el paseo.
besides()
A preposition is a word that indicates the relationship between a noun and another word (e.g., He ran through the door.).
1. (apart from)
a. además de
Besides the toiletries, I have to buy a new bathing suit for the trip.Además de los artículos de tocador, tengo que comprar un nuevo traje de baño para el viaje.