The film's description coupled with the main picture can be misleading as the young man shown, Jameson Parker, and the older lady, Rita Moreno, are mother and son playing tennis together. Susan Flannery, who plays Moreno's best friend, is the main character/divorced woman who has the titular seduction/affair with the younger man, Jameson.
Though the movie is about a middle age woman having an affair with a college student half her age, in real life Jameson Parker was only eight years younger than Susan Flannery.