LGBT: These initials stand for "lesbian, gay, bisexual, and transgender." During the past 20 years, the phrase "LGBT community" has replaced "gay community" and can also refer to a broader concept of gender identity and sexuality.

Mattachine Society: The oldest continuously operating gay-rights organization in the United States, founded in 1950. During medieval times, the "Mattachine" were court jesters who, unlike almost anyone else, were free to make pointed social commentary. In the mid-20th century, when gay people (and any talk of homosexuality) were closeted, a group of gay men working toward equal rights—recognition of the truth of the existence of homosexuality—named themselves after the jesters of long ago. Since the 1950s, "Mattachine" has become a generic term for gay-rights groups.

SAGE: An acronym that stands for "Services and Advocacy for GLBT Elders," an organization founded in 1978 (and historically known as "Senior Action in a Gay Environment") to promote awareness of and to help LGBT people age 50+. SAGE is one of the oldest and largest nonprofit agencies to serve older lesbian, gay, bisexual, and transgender people.

Stonewall Riots: A series of spontaneous demonstrations that started after a police raid on the Stonewall Inn on June 28, 1969 and which continued during several days in New York’s Greenwich Village. The riots marked the beginning of the gay liberation movement and were commemorated the following year in the first Gay Pride events in New York and Los Angeles.