his/her/their invitation; your invitation (formal)
Thank you for your invitation.
Me da gusto aceptar su invitación.
I am pleased to accept your invitation.
McCaulayson recibió su invitación personal a la inauguración.
McCaulayson received his personal invitation to the opening.
Did you accept their invitation?
He did not accept her invitation.
Tom no sabía la razón de por qué Mary no aceptaba su invitación.
Tom didn't know why Mary wouldn't accept his invitation.
No puedo dejar de aceptar su invitación.
I cannot refuse your invitation.
She declined his invitation.
I accepted his invitation.