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"Then" is an adverb which is often translated as "entonces", and "one moment" is a phrase which is often translated as "un momento". Learn more about the difference between "then" and "one moment" below.
then()
An adverb is a word that describes a verb, an adjective, or other adverbs (e.g., to run quickly, very tired).
a. entonces
If you eat healthy food, then you won't get sick.Si comes comida sana, entonces no te enfermarás.
one moment()
A phrase is a group of words commonly used together (e.g., once upon a time).
1. (general)
a. un momento
There was one moment in the debate that I am sure people will be talking about for days.Hubo un momento en el debate del que estoy seguro que la gente va a estar hablando durante días.
b. un instante
He was there one moment and then gone the next.Estaba allí un instante y luego se había desaparecido.