Usage Note
Sus is the plural possessive determiner used before nouns, corresponding to su (singular). It covers 'his', 'her', 'its', 'their', and formal 'your' (usted/ustedes) — context determines which. Because Spanish does not distinguish these in the possessive, sus libros could mean his books, her books, their books, or your (formal) books. Contrast with the stressed possessive pronouns suyos/suyas used after a noun or standing alone.
Examples
"Sus hijos juegan en el parque."
Natural Translation
His/her/their children play in the park.

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