I'd like to share the definitions I operate from when working with LGBT clients and issues.
Sex-
What we are assigned at birth. Believed to be binary (male or female)
and to dictate gender expression. In reality, many are born intersexed,
and/or experience a gender that is different from their birth-assigned
sex. Gender-Socially constructed, learned via
culture. In Western culture typically binary: men (who are masculine)
and women (who are feminine). Behavior, appearance, and societal roles
are differently defined for each gender. For most people, gender is
their sex made visible. For transgender, gender variant or gender
non-conforming people this is not the case. Sexual Orientation - A person's sexual/romantic attraction to members of the same and/or opposite sex. Includes gay, lesbian, bisexual and heterosexual. Gender Identity - A person's inner sense of self as male, female
or other gendered. Gender identity may not
corresponds to the sex you were assigned at birth. (People often confuse sexual orientation and gender identity. Your
gender, whether it is man, woman, transgender, says nothing about your sexual orientation.) Gender Expression- The way people communicate their gender identity to others through behavior and
appearance. Transgender people may desire to make their gender expression match their internal identity, rather
than their birth-assigned gender or sex. Transgender- An umbrella term that
can be used to refer to a variety of identities that do not
conform to the gender role expectations of their birth-assigned sex. It
may include people who identify as transexuals, female-to-male
(FTM),male-to-female (MTF). genderqueer or other gendered. Transgender
people may or may not choose to alter their bodies hormonally and/or
surgically.
For further definitions of many sexual orientation/gender
identity related terms see: Glossary or Trans Basics: Glossary of Terms (note: terms are constantly evolving. the only way to be certain which terms an individual prefers is to ask!)