Human sexuality is complex. The acceptance of the distinction between desire, behaviour, and identity acknowledges the multidimensional nature of sexuality. The fact that these dimensions may not always be congruent in individuals suggests the complexity of the issues.
Bisexuality, both sequential and concurrent, and discordance between biological sex and gender role and identity add to the issues. Medicine and psychiatry employ terms like homosexuality, heterosexuality, bisexuality, and trans-sexuality to encompass all related issues. At the same time, current social usage argues for lesbian, gay, bisexual, and transgender (LGBT), which focuses on identities.
The prevalence of homosexuality is difficult to estimate for many reasons, including the associated stigma and social repression, the unrepresentative samples surveyed, and the failure to distinguish desire, behaviour, and identity. The figures vary between age groups, regions, and cultures.
Medicine and science continue to debate the relative contributions of nature and nurture, biological and psychosocial factors, to sexuality. Essentialist constructs argue for biology and dismiss personal and social meanings of sexual desire and relationships.
On the other hand, constructivists support the role of culture and history. While essentialism and constructionism, on the surface, appear contradictory, they may mediate orientation and identity, respectively.
Anthropologists have documented significant variations in the organization and meaning of same-sex practices across cultures and changes within particular societies over time.
The universality of same-sex expression coexists with variations in its meaning and practice across cultures. Cross-cultural studies highlight the limits of any single explanation of homosexuality within a particular society. Classical theories of psychological development hypothesize the origins of adult sexual orientation in childhood experience.
However, recent research argues that psychological and interpersonal events throughout the life cycle explain sexual orientation. It is unlikely that a unique set of characteristics or a single pathway will explain all adult homosexuality.