Educational Content: This article is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider for diagnosis and treatment.

Definition of Sub

Medically reviewed by Dr. Otari Nergadze, Neurosurgeon | Updated: January 2026

Sub-: Prefix meaning meaning under, below, less than normal, secondary, less than fully. As in subacute, subaortic stenosis, subarachnoid, subclavian, subclinical disease, subcutaneous, subdural, subglottis, subjacent, sublingual, subluxation, and subtotal hysterectomy. From the Latin preposition sub meaning under.

See also: Hypo-.

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