Demigender (from demi "half" + "gender") is an umbrella term for nonbinary gender identities that have a partial connection to a certain gender. This includes the partly female identity demigirl, and the partly male identity demiboy. There are other partial genders using the "demi-" prefix for the same reasons. For example, deminonbinary, demifluid, demiflux, and so on. Like nonbinary, demigender is also an identity within itself, for people who feel connection to the concept of gender rather than certain genders. Being a demigender "is not dependent on how much (as in percentage) someone identities as one gender; it solely depends on if a person identifies as partially. For some, they may identify with two or more genders while others may not."
A demigirl is someone who only partially (not wholly) identifies as a girl or woman, whatever their assigned gender at birth. They may or may not identify as another gender in addition to feeling partially a girl or woman. May also use the terms demigal, demifemale or demiwoman.
Alternatively, demigirl can be used to describe someone assigned female at birth who feels but the barest association with that identification, though not a significant enough dissociation to create real physical discomfort or dysphoria, or someone assigned male at birth who is trans feminine but not wholly binary-identified, so that they feel more strongly associated with “female” than “male,” socially or physically, but not strongly enough to justify an absolute self-identification as "woman". Continue reading from Nonbinary Wiki