Neutral is a segment resting in the middle of its range without effort.
A pelvis, a ribcage, a head, a shoulder blade: each has a place it can sit without extra arch, tuck, lift, or brace. 📝Neutral Spine is the spinal version of the same idea. In 📝Postural / Structural Realignment neutral is a place to visit, not a pose to freeze in all day, and not a moral ideal of posture. Everyone's middle is personal.
Clients often confuse it with tucking, with military chest-out, or with holding still. Cueing is usually less effort, not a new grip. Pain or numbness when they try to find it is a stop.