The word cisgender or cis refers to people who identify with the sex or gender they were assigned at birth. The word is used within trans activism in an inclusive way to refer to non-transgender people. Cisgender people do not usually identify themselves as cisgender; this consistency in gender identity is implicit in cis-heteronormativity or cis-homonormativity.
The prefix cis etymologically means ‘on the side of’ and it is the opposite of the prefix trans, which means ‘on the other side’. Calling someone cisgender does not imply a political ideology or a specific gender expression. The purpose of the prefix cis is to highlight and dismantle the binary hierarchical distinction and its discrimination towards the LGBTIQ+ collective, specifically towards the trans community. Sexual orientation is not part of this term. Therefore, a cisgender person can be gay, lesbian, asexual, etc.