Intersex is a term for those born with physical sex characteristics that cannot be traditionally classified as wolffian (male) or müllerian (female).^[1] Variations may appear in a individual’s chromosomes, hormones, genitalia, gonads, secondary sex characteristics, or some combination of these things.

Intersex variations are observed in many animals including humans. According to the ISNA it is estimated that as many as 1.7% of individuals are born with intersex traits, however this may be an incorrect estimate, as many individuals are unknowingly intersex due to the fact that external genitalia is the only sex characteristic noticed at birth (in most cases).^[2][3]

Intersex does not describe a specific body type but rather is an umbrella term for a broad range of variations/traits. Some intersex individuals may closely resemble one of the binary sexes, while others are closer to in between. An intersex individual may have characteristics of both the wolffian and müllerian sexes, characteristics that fall somewhere in-between wolffian and müllerian, and/or characteristics that don't fall into either.

Intersex individuals may have any gender identity, including male, female, non-binary, etc.^[4] They may identify as cisgender or transgender, or possibly another gender modality such as ipsogender or ultergender. Intersex individuals can have any assigned gender at birth, some may be AMAB or AFAB because their variation of intersex was not noticed at birth. Others may be coercively assigned male/female at birth (CAMAB/CAFAB), meaning they had nonconsensual surgery preformed on them so their body more closely fits one of the binary sexes. In some rare cases they are AXAB. Each intersex individual has a unique relationship to their gender, assigned gender at birth, the gender they were raised as, and how that relates to their experience being intersex.

Intersex is included in the LGBT+ community, though not all intersex individuals consider themself to be LGBT+ on the basis on being intersex. This is largely a personal choice based on how one's status as intersex has (or hasn't) affected their experiences.

Someone who is not intersex is called dyadic, perisex, or endosex. Intersex is not an identity, but is something one is born as. Some intersex traits are identified at birth, while others may not be discovered until puberty or later in life (although, the variation was always present, just unnoticed). One cannot "transition to intersex". Dyadic individuals who desire mixed sex traits may identify as altersex.