su argumento

his/her argument

→ su
phrase Rare #37,735
his/her argument su can mean his, her, your, or their depending on context; argumento means argument or reasoning.
SP: Su argumento fue muy convincente.
EN: His argument was very convincing.

Su argumento es más radical que el suyo.

His argument is more radical than yours.

Su argumento era lógico.

His argument was logical.

Su argumento es lógico.

His argument is logical.

Su argumento carece de lógica.

His argument lacks logic.

Su argumento es convincente.

His argument is convincing.

— Porco Rosso (1992)