How to Say "endlessly" in Spanish
The Spanish word for “endlessly” is “eternamente” — B1 level. This is a very common word in everyday Spanish.

Examples
Te estaré eternamente agradecido por tu ayuda.
I will be forever grateful to you for your help.
Prometieron amarse eternamente.
They promised to love each other eternally.
La película fue tan aburrida que pareció durar eternamente.
The movie was so boring that it seemed to last forever.
The '-mente' Suffix
This word is formed by taking the adjective 'eterna' and adding '-mente.' This is exactly like adding '-ly' to an English adjective to describe how an action is done.
Keeping the Feminine Form
When you build these types of words, you always start with the feminine (ending in -a) version of the adjective. That's why it is 'eternamente' and not 'eternomente'.
Placement in the Sentence
Mistake: “Using it before the subject like 'Eternamente yo te amo'.”
Correction: It usually sounds more natural after the verb: 'Te amo eternamente' or 'Estaré eternamente agradecido'.
Related Translations
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