How to Say "for free" in Spanish
The Spanish word for “for free” is “gratis” — A1 level. This is a very common word in everyday Spanish.

Examples
La entrada al museo es gratis los domingos.
Entrance to the museum is free on Sundays.
Si compras dos, te dan la tercera unidad totalmente gratis.
If you buy two, they give you the third unit completely free.
Con el servicio premium, el envío es gratis.
With the premium service, shipping is free.
Always Unchanging
'Gratis' never changes its form. It always stays 'gratis' regardless of whether the thing you got is masculine, feminine, singular, or plural. (It is 'invariable').
Adverb vs. Adjective
While it describes a noun (like 'free delivery'), 'gratis' functions as an adverb, describing the manner of the transaction, which is why it doesn't need to match the noun.
Adding Plural Endings
Mistake: “Las bebidas son gratises.”
Correction: Las bebidas son gratis. (Never add an -s, even if you are talking about many things.)
Related Translations
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