“A sense of awareness, usually beginning in infancy, continuing throughout childhood, and reaching maturity in adolescence, of being male or female, or of the gender associated with one’s biological sex.” (Gender Identity, 2001).
“The relative degree to which an individual patterns himself or herself after members of the same sex.” (Barker, 2003, p. 174).
Related: Sexual Identity: “The degree to which an individual takes on the behaviors, personality patterns, and attitudes that are usually associated with male or female sex roles. (Barker, 2003, p. 394).

"gender identity n." Colman, A.M. (2001). A dictionary of psychology. [Online]. Oxford: Oxford University Press. Oxford Reference Online. BLC Boston College Libraries. Retrieved June 9, 2005, from *Note, a subscription is required to access this link. Barker, R.L. (2003). The social work dictionary (5th ed.). Washington, DC: NASW Press.