Gender identity: Our internal, personal sense of what our gender is. Everyone has a gender identity.
Cisgender: A person who identifies with the sex they were assigned at birth.
Transgender (trans): An umbrella term used to describe people whose true gender identity does not “match” the sex or gender they were assigned at birth. … Many identities fall under the transgender umbrella. However, not all genderqueer or non-binary people identify as transgender – and some people who have transitioned to their true gender choose to identify as just a “man” or “woman” instead of transgender.
Binary system: A binary system is something made up of two opposing parts. Gender (man/woman) and sex (male/female) are examples of binary systems.
Non-binary: Anything that falls outside of the binary system. Intersex, genderqueer, and bisexuality are all examples of non-binary identities.
Definitions from The Trevor Project.