Sexual orientation refers to an enduring pattern of emotional, romantic, and/or sexual attractions to men, women, or both sexes, or neither sex. It also encompasses an individual's sense of identity based on those attractions, related behaviours, and membership in a community of others who share those attractions. Common sexual orientations include heterosexuality (attraction to the opposite sex), homosexuality (attraction to the same sex), bisexuality (attraction to both sexes), and asexuality (lack of sexual attraction to others). Sexual orientation is generally understood to be a fundamental aspect of personal identity and is distinct from gender identity and gender expression.