I met them at a dinner party. - Onlarla bir akşam yemeği partisinde tanıştık.
Tom is at a dinner party. - Tom bir akşam yemeği partisinde.
A relatively formal meal at which invited guests eat in the home of the host; a guestmeal
A dinner party is a social event where a small group of people are invited to have dinner and spend the evening at someone's house. a social event when people are invited to someone's house for an evening meal