Ningender (shortened to NIN) is an umbrella term for all genders which are neutral in nature (NIN). It can be used as an umbrella term for any genders that are primarily related to a gender quality that is not masculine or feminine. This includes genders such as neutrois, stellarian, maverique, and other unaligned/abinary/neutral aligned non-binary genders.
NIN is not necessarily synonymous with non-binary, because some non-binary genders can be feminine or masculine aligned. For example, juxera is a non-binary gender but it is feminine in nature (fingender), not neutral.
Ningender can also be used as a gender on its own, referring to any gender that isn't fully defined by being neutral but is still related to neutralness, or a gender in which neutralness is its defining feature. It's often used by people who cannot narrow down their gender any more than being neutral or non-binary.
The masculine equivalent is mingender. The feminine equivalent is fingender. The androgynous equivalent is lingender. The genderless equivalent is agingender.