In semiotics the neutral level is the "trace" left behind, the physical or material creation of esthesic and poietic, productive or creative and receptive or perceptive, processes.
In mains wiring, neutral has two subtly different meanings. The first meaning refers to a current-carrying core that is tied to a grounding point. The second refers to a core that acts as a common for several phase cores.
In language study, neutral is an adjective used for the neuter noun gender, as well as for the gender-neutral language.