There are multiple definitions:
Herfindahl-Hirschman Index(English)
- the sum of squared market share of patient visits in destination ZIP codes within each CSA, and a higher HHI indicates more concentrated (as opposed to competitive) market
- CSA
- Health care industry
- https://doi.org…tbs.2021.05.003
horizontal head-impulse [test](English)
- the head is turned in the yaw plane by 10–20° at high acceleration and velocity (typically exceeding 300°/s) while the subject maintains visual fixation on a stationary object. A refixation saccade (or series of corrective saccades) is thought to indicate a deficit in lateral canal function on the side with ampullopetal stimulation
- SCT, VOR
- Neurology, Ophthalmology, Disability
- https://doi.org…016480701299642