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"Sinceramente" is an adverb which is often translated as "sincerely", and "la verdad es que" is a phrase which is often translated as "the truth is that". Learn more about the difference between "sinceramente" and "la verdad es que" below.
sinceramente()
An adverb is a word that describes a verb, an adjective, or other adverbs (e.g., to run quickly, very tired).
1. (genuinely)
la verdad es que()
A phrase is a group of words commonly used together (e.g., once upon a time).
1. (general)
a. the truth is that
La verdad es que yo escondí tus cigarrillos porque quiero que no fumes.The truth is that I hid your cigarettes because I don't want you to smoke.