Black tie is sometimes referred to as 'dinner jackets', 'dress for dinner' and 'cravate noir' or, in America, as 'tuxedos.'
Traditional black tie for men consists of:
• Black wool dinner jacket. Single-breasted with no vents, silk peaked lapels (or a shawl collar) and covered buttons.
• Black trousers - slightly tapered - with a single row of braid down each outside leg.
• White marcella evening shirt with a soft turn-down collar, worn with cufflinks and studs.
• Black bow tie must be hand tied; avoid novelty ties or colours.
• Highly polished or patent black lace-up shoes.
• Black silk socks, long enough to ensure that no leg will show between the trouser leg and sock when seated.
• A white silk scarf is an optional but traditional accessory.
Top Tip: cummerbands or low cut black evening waistcoats are rarely worn nowadays.
For ladies, a smart dress (such as a cocktail dress) is appropriate. It can be long or short, as long as it's not too short. It need not be black.