A possessive adjective accompanies a noun.
mi envío - my shipment tu beneficio - your benefit nuestro arreglo - our arrangement su sinceridad - his, her, their or your sincerity su padre - his, her, their or your father sus padres - his, her, their or your parents sus fondos - his, her, their or your funds
mi libro - my book mis dos libros - my two books
The nosotros and vosotros forms change in gender as well;
nuestro libro - our book nuestra mesa - our table
nuestras familias - our families nuestros refrescos - our soft drinks