The New American Heritage dictionary defines middle age as "the period between youth and adulthood, generally 40 to 60." The Oxford English Dictionary cites 45 to 60, while Webster's and the U.S. Census Bureau peg middle age at 45 to 64. The nonprofit Pew Research Center uses 50 to 64 (dubbing it the "threshold generation") and classifies those between 30 and 49 in its "younger adult" category.