Formal & Grand:
* Soirée: A formal evening party, often with a specific theme.
* Ball: A formal dance, often held for charity or a special occasion.
* Fete: A festive celebration, often outdoors and with a specific theme.
* Celebration: A general term for any event marking a special occasion.
* Ceremony: A formal event with a specific purpose, often involving speeches and rituals.
* Spectacle: A public event that is designed to be impressive or entertaining.
Informal & Fun:
* Party: A social gathering for entertainment or celebration.
* Bash: An informal and lively party.
* Do: A British term for a party or social event.
* Gathering: A group of people assembled for a specific purpose.
* Festivities: A series of events that are part of a celebration.
The best word to use will depend on the specific context and the tone you want to convey.