Gender is most often attributed to human beings or mammals as a dynamic, complex aggregate of learned behaviors and social or cultural constructs. Gender is distinguished from physiological and reproductive sexual traits, i.e. that individuals are male or female. While sexual designations are widely used in the Animal, Plant and even Fungal Kingdoms, it is less common to find descriptions outside the Animal Kingdom invoking femininity and masculinity. Non-animals have simply not been shown to have sufficient cognitive or behavioral complexity to exhibit gender, per se. Gendered descriptions are more commonly applied by humans to other humans and to other animals, especially to the more intelligent, social mammals which form communities such as packs of wolves. There are also clear examples of gendered behaviors, even gender stereotypes, among birds such as the elaborate mating rituals of bower birds, the territoriality of roosters, and the dramatic displays of peacocks. 
Among humans, the concept of gender is complex and more recently the study of gender expression has shown that gender identification is multivariate and, in the case of transgender or transsexual persons, may not be aligned with anatomical determinants. Sexual orientation is a distinct characteristic from gender identification. Cultural and political affiliations between minority groups, as found in the lesbian-gay-bisexual-transgender (LGBT) designation, may inadvertently conflate gender with sexual orientation. Conceptualizing gender as a spectrum rather than as a dichotomy gained increased acceptance in the late twentieth century.
- It should also be noted that intersexual and asexual traits can be found in animals, plants, and fungi making distinctions of an organism as either male or female, masculine or feminine, not always meaningful or accurate. See Androgyny.