The Lost Generation is the generation that came of age during World War I. Demographers William Strauss and Neil Howe outlined their Strauss–Howe generational theory using 1883–1900 as birth years for this generation. The term was coined by Gertrude Stein and popularized by Ernest Hemingway, who used it as one of two contrasting epigraphs for his novel The Sun Also Rises. Hemingway credits the phrase to Gertrude Stein, who was then his mentor and patron.