Closeted and in the closet are adjectives for lesbian, gay, bisexual, transgender etc. ( LGBT) people who have not disclosed their sexual orientation or gender identity and aspects thereof, including sexual identity and sexual behavior. It can also be used to describe anyone who is hiding part of their identity because of social pressure.
In late 20th-century America, the closet had become a central metaphor for grasping the history and social dynamics of gay life. The notion of the closet is inseparable from the concept of coming out. The closet narrative sets up an implicit dualism between being "in" or being "out". Those who are "in" are often stigmatized as living false, unhappy lives. However, though many people would prefer to be “out” of the closet, there are numerous social, economic, familial, and personal repercussions that lead to them remaining, whether consciously or unconsciously, “in” the closet. The decision to come out or remain in the closet is considered a deeply personal one, and outing remains controversial in today’s culture.
In the 21st century, the related concept of a "glass closet" emerged in LGBT discourse.  This term describes public figures, such as entertainers or politicians, who are out of the closet in their personal lives and do not engage in the tactics (such as entering a lavender marriage or publicly dating a person of the opposite sex as a "beard") that were historically used by closeted celebrities to disguise their sexual identity, but have not formally disclosed their sexual orientation on the public record — and who, thus, are technically neither fully in the closet nor fully out of it. 
In the early stages of the lesbian, gay or bisexual identity development process, people often feel confused and experience turmoil. In 1993, Michelangelo Signorile wrote Queer in America , in which he explored the harm caused both to a closeted person and to society in general by being closeted.
Seidman, Meeks, and Traschen (1999) argue that "the closet" may be becoming an antiquated metaphor in the lives of modern-day Americans for two reasons.
- Homosexuality is becoming increasingly normalized and the shame and secrecy often associated with it appear to be in decline.
- The metaphor of the closet hinges upon the notion that stigma management is a way of life. However, stigma management may actually be increasingly done situationally.
The closet, however, is difficult for any non-heterosexual, non- cisgender identified person to fully come "out" of, whether or not that person desires to do so. Scholar Eve Kosofsky Sedgwick, author of the Epistemology of the Closet , discusses the difficulty with the closet:
- “the deadly elasticity of heterosexist presumption means that, like Wendy in Peter Pan, people find new walls springing up around them :even as they drowse: every encounter with a new classful of students, to say nothing of a new boss, social worker, loan officer, landlord, :doctor, erects new closets.”
Recent attention to bullying of LGBTQ youth and teens in the United States gives an indication that many youth and teens remain closeted throughout their educational years and beyond for fear of disapproval from parents, friends, teachers, and community members. To remain in the closet offers an individual a layer of protection against ridicule and bullying. However to remain in the closet typically takes a toll on the mental health of the individual, especially in the adolescent years as reflected in suicide rates among LGBTQ youths. 
- Down-low (sexual slang)
- Ego-dystonic sexual orientation
- National Coming Out Day
- The Closet (2001 film)
- Terry Dolan (activist)
- Seidman, Meeks, and Traschen (1999)
- . www.out.com . 2008-09-23 . Retrieved 2016-06-12 .
- re-released in 2003 by University of Wisconsin Press, ISBN 0-299-19374-8
- Sedgwick, Eve Kosofsky. The Epistemology of the Closet .
- . www.lambda.org . Retrieved 2016-06-12 .