Base of support is the area under and between the feet that the body balances over.
Narrow it — feet together, or standing on one foot — and the rest of the body has to work harder to stay up. Widen it, or feel the whole sole, and stacking upward has somewhere to start. In 📝Postural / Structural Realignment grounding through that base is often the first cue, because a pelvis and ribcage cannot organize over a foot that is not there. This is a gravity finding, not a diagnosis of balance disease.
Clients feel it as weight in the heels, the toes, or the inner arch, and as a sway they did not notice until they looked. Practice is feeling the contact, not gripping the floor.
Dizziness, falling, or a sudden change in how the feet take weight is a referral.