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

Examples
Definitivamente es la mejor película del año.
It is definitely the best movie of the year.
¿Vienes con nosotros? — Sí, definitivamente.
Are you coming with us? — Yes, definitely/absolutely.
Ella decidió definitivamente no volver a fumar.
She decided conclusively (or 'for good') not to smoke again.
The '-mente' Adverb Pattern
Adverbs like 'definitivamente' are formed by taking the feminine form of an adjective ('definitiva') and adding the ending '-mente'. This works just like adding '-ly' to an adjective in English (definitive -> definitively).
Placement for Emphasis
Mistake: “Sometimes learners put 'definitivamente' inside the verb phrase, like 'Yo he definitivamente comido' (Incorrect word order).”
Correction: In Spanish, adverbs usually go before the verb, after the verb, or at the start of the sentence for emphasis: 'Yo definitivamente he comido' or 'Definitivamente he comido.' (Correct usage).
Related Translations
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