The Basics
The word “trans” comes from a Latin word meaning “across.” For example, a trans-Atlantic flight goes across the Atlantic Ocean; a transnational issue affects people all across the country; and so on.
"Transgender" literally means “across gender.” We use ‘trans’ today as an umbrella term to describe those whose gender identity differs somehow from the gender they were given at birth.
The word “cis” comes from a Latin word meaning “the same side.” Cisgender is a term used to describe someone whose gender has not changed from the one they were given at birth.