A category of sexual orientation, defined by sexual or romantic attraction toward two or more genders. The vocabulary of bisexual has been a stable component of international LGBTQ+ orientation-categorisation since the late 20th century, with substantial conceptual development through the Kinsey Scale, the Klein Sexual Orientation Grid, and the broader sex-research-and-orientation-studies literature.

Overview

Bisexual (often abbreviated bi; Japanese: バイセクシュアル, baisekushuaru; from Latin prefix bi-, “two”, + sexualis, “of sex”) is the sexual-orientation category for sexual or romantic attraction toward two or more genders. The category sits within the broader LGBTQ+ orientation-vocabulary as one of the principal orientation-categories alongside gay, lesbian, pansexual, asexual, and others.

The term has two layered usage-registers. In its older and narrower interpretation, bisexual denoted attraction to both “men” and “women” within a binary-gender framework. In its contemporary broader interpretation, the bi- prefix is read as denoting attraction to one’s own gender and other genders, with the gender-vocabulary not necessarily restricted to a binary framework. Contemporary bisexual-community-and-research positions broadly hold that the term is compatible with non-binary-gender frameworks and inclusive of attraction to a wide range of genders.

The category sits adjacent to and overlaps with several others. Pansexual (sexual or romantic attraction independent of gender) and polysexual (attraction to multiple genders but not all) are the principal adjacent categories. The choice between bisexual and pansexual self-identification is, for many individuals, a matter of personal-choice, generational-reading, and community-affiliation rather than a strict-conceptual difference.

Etymology

The English term bisexual originated in the late-19th-century biological literature, where it described biological organisms with both male and female reproductive structures (hermaphroditism in the technical sense). Through the early 20th century, Freudian psychoanalytic theory developed the concept of universal bisexuality — the idea that all humans have latent attraction to both genders, with overt orientation as a specialisation of this latent capacity.

The mid-20th-century sexology research, particularly the work of Alfred Kinsey, brought the concept of orientation as a continuum into mainstream research. The Kinsey Scale (Sexual Behavior in the Human Male, 1948; Sexual Behavior in the Human Female, 1953) classified sexual orientation on a 0-to-6 continuum from fully-heterosexual to fully-homosexual, with the middle range establishing bisexuality as a recognised independent category in the broader research framework.

Through the 1970s, the term bisexual established itself as a self-identification term in Anglophone gay-and-lesbian-rights movements, alongside the broader emergence of identity-affirming orientation-vocabulary. Fritz Klein’s The Bisexual Option (1978) and the Klein Sexual Orientation Grid (KSOG, 1980s) provided multidimensional frameworks for understanding bisexuality beyond the simple-continuum framework of the Kinsey Scale.

Historical development

International movement history

Bisexual movement organisation in the United States proceeded through the 1980s and 1990s. BiPOL (1983, the first U.S. bisexual political organisation), the International Bisexual Conference (first held 1990), and Celebrate Bisexuality Day (established 1999, observed on September 23) established the contemporary movement-infrastructure for the bisexual community.

Within the broader LGBTQ+ movement-history, bisexual community members have historically navigated a doubled-marginal-position. Critique from gay-and-lesbian movement contexts has sometimes characterised bisexual identity as compromised by access to “heterosexual privilege”, while heteronormative-context critique has sometimes treated bisexual identity as either non-serious or as “covering” for actual gay-or-lesbian identity. The phenomenon of bisexual erasure (the systematic non-recognition of bisexual identity in social contexts) is a continuing topic in bisexual-community advocacy and research literature.

Visibility in Japan

The category-vocabulary of bisexual (and the corresponding Japanese-language adaptation baisekushuaru) entered Japanese-language usage primarily through the late-1990s influx of Anglophone LGBTQ+ movement vocabulary. Prior to this period, individuals with attraction-patterns extending across multiple genders generally lacked dedicated identity-vocabulary in Japanese-language contexts, with the broader categories of gay, lesbian, and non-ke (heterosexual) being the principal organisation of orientation-vocabulary.

Japanese gay-publication culture (the magazine Barazoku, 1971-2008; Sabu, 1974-2002) included reader-contributions and accounts from individuals with bisexual experiences, indicating the existence of a bisexual community in latent form even in periods predating the contemporary identity-vocabulary. Explicit bisexual self-identification in Japan stabilised after the late-1990s adoption of the Anglophone movement vocabulary.

Through the 2000s, dedicated Japanese bisexual community organisations and self-help groups (BiTOPIA, BNet Kantō, others) emerged, with focus on community-interaction-and-mutual-support, social-visibility, and participation in the broader LGBTQ+ movement.

Same-sex partnership and the LGBT Awareness Promotion Act

The 2015-onward expansion of municipal-level same-sex partnership systems in Japan (covering 459 municipalities as of June 2024, with population-coverage above 85%), and the June 2023 Act on Promotion of Public Understanding of Diverse Sexual Orientation and Gender Identity, have produced substantial general-social-visibility increases for the broader LGBTQ+ population including bisexual individuals.

The implementation of these frameworks has, however, typically referenced the broader LGBTQ+ category rather than addressing bisexual-specific issues directly. Bisexual-specific social-recognition-issues (the bisexual-erasure phenomenon, the doubled-community-belonging condition) have received relatively limited explicit policy-level attention, with most contemporary policy treating bisexuality within the broader LGBTQ+ umbrella.

Frameworks for measurement

Kinsey Scale

The Kinsey Scale (1948) classifies orientation on a 7-point continuum:

• 0: exclusively heterosexual
• 1: predominantly heterosexual, occasional homosexual experience
• 2: predominantly heterosexual, more than incidental homosexual experience
• 3: equally heterosexual and homosexual
• 4: predominantly homosexual, more than incidental heterosexual experience
• 5: predominantly homosexual, occasional heterosexual experience
• 6: exclusively homosexual
• X: no sexual interest (asexual)

The Kinsey Scale provided the first widely-used framework in which bisexual orientation was treated as a distinct continuum-category between heterosexual and homosexual orientation, displacing the binary-orientation framework.

Klein Sexual Orientation Grid

Fritz Klein’s KSOG (1980s) extended the Kinsey Scale’s single-continuum framework into multiple dimensions. The KSOG measures orientation on seven separate axes — sexual attraction, sexual behaviour, sexual fantasies, emotional preferences, social preferences, self-identity, and lifestyle — across three time-points (past, present, ideal). The framework allows orientation to be described as the combination across these multiple axes, with bisexual orientation potentially distributed differently across the axes for any given individual.

The KSOG provides one of the more conceptually-rigorous frameworks for bisexual orientation, recognising that bisexual identity does not require equal-distribution across the axes and accommodating the substantial individual-variation in how the bisexual-orientation register is configured for different individuals.

Contemporary perspectives

Contemporary sexual-orientation research increasingly treats orientation as a fluid, continuous, and multidimensional rather than fixed-and-categorical phenomenon. Bisexual identity sits within this broader research framework as one of several valid self-identifications individuals may adopt within their orientation-experience.

Bisexual and pansexual

The relationship between bisexual and pansexual is a recurring topic in contemporary orientation-discourse. The two categories overlap substantially in their working denotations of attraction-across-multiple-genders but distribute somewhat differently across community contexts.

Pansexual (defined as attraction to all genders, with gender not as the determining factor in attraction) emphasises gender-independence in the orientation. Bisexual, in its older binary-gender reading, emphasised attraction to both major genders within a binary framework; in its contemporary broader reading, accommodates attraction to multiple genders in a way that is largely indistinguishable from pansexual.

The contemporary individual self-selection between the two categories tends to track generational-and-community factors. Younger individuals who came to identity-consciousness in the 2000s-onward period often select pansexual; older individuals from the 1980s-90s movement-period often retain bisexual. The selection reflects (1) the individual’s relationship to gender-binary frameworks, (2) the individual’s affiliation with established community organisations, and (3) the individual’s reading of the historical-and-political content of the term.

Bisexual erasure and community position

The bisexual erasure phenomenon — the systematic non-recognition of bisexual identity in everyday social contexts — has been documented in multiple studies of bisexual individuals’ social experience. The phenomenon operates through the social-default assumption that an individual in a different-gender relationship is heterosexual and an individual in a same-gender relationship is gay or lesbian, with the bisexual identity therefore non-visible in either configuration.

This invisibility has correlated, in multiple research studies, with elevated rates of depression, anxiety, and self-harm among bisexual individuals relative to gay-and-lesbian individuals. The structural-marginal-position of bisexual identity within the broader LGBTQ+ community-context has produced dedicated bisexual community organisations and support structures specifically addressing this doubled-marginal condition.

Cultural reference

Literary and film representation of bisexual identity has expanded substantially through the late 20th and early 21st centuries. Works such as Rita Mae Brown’s Rubyfruit Jungle (1973), Audre Lorde’s autobiographical writings, and Virginia Woolf’s Orlando (1928) provide canonical literary representations. Films such as Brokeback Mountain (2005), Carol (2015), and Call Me by Your Name (2017) have brought representations of bisexual experience to substantial international audience attention.

Adult-content note

This entry treats bisexuality as a sexual-orientation category, not as a sexual-content tag-category. The use of bisexual in adult-content classification systems for content depicting sexual-and-romantic relationships across gender combinations exists but is conceptually distinct from bisexual identity as a real-world orientation. The entry’s framework prioritises the orientation-and-identity dimension and treats the adult-content tag as adjacent rather than central.

Related Terms

• Gay
• Lesbian (rezu)
• Asexual
• Demisexual
• Newhalf
• Yuri
• Boys’ Love