A ball is a formal dance occasion. By formal is meant: people were invited, wore their best clothes ('evening attire'), and the ball was held in a splendid ballroom. In former times everyone danced, but only the wealthy went to balls. Girls had dance cards: men had to sign up to dance with them. Older people sat around the sides and watched the younger people dance. It was a society occasion.
A ball at Apsley House. Shows King Edward VII and Queen Alexandra dancing a quadrille, 1908.
Mardi Gras Ball, 1930s
by William Hogarth, 1745
Palacio San Martín, Buenos Aires
Ballroom of the Fairmont Royal York Hotel, Toronto
Ballroom of the Canals family mansion, Tarragona
The ballroom of the Catherine Palace, near St Petersburg