Demigender is a group of genders in which one is partially, but not fully, a given gender. It can also describe those who feel the barest connections to a gender, but not enough to fully identify as that gender. Demigender people may identify as another gender in combination with demigender. Demigender can also be an identity in itself, for people who feel a partial connection to the concept of gender in general. Demigender people often identify as non-binary and may also identify as transgender.
Being demigender does not necessarily mean that one is partially a given gender and partially agender (though it can be). One can be, for example, a demiboy and a demigirl at the same time, meaning part of one's gender is boy and the other part is a girl. The "other part" of one's gender can be any gender or combination of genders.
The opposite of demigender is hypergender.
Similar genders include libragender and paragender.
Any gender can have a demigender version of it, usually created by adding the demi- prefix in front of the gender.