| Term | Definition |
| Hyperacidity | Excessive acidity |
| Hypoacidity | Weak acidity |
| Hyperglycemia | Excess of sugar in the blood |
| Hypoglycemia | Abnormally low level of sugar in the blood |
| Hypertension | Abnormally high blood pressure |
| Hypotension | Low blood pressure |
| Hyperthermia | Especially high fever; hyperpyrexia |
| Hypothermia | Subnormal body temperature |
| Hyperthyroid | Marked by excessive activity of the thyroid gland |
| Hypothyroid | Marked by deficient activity of the thyroid gland |
| Hyperactive | Overactive |
| Hyperbole | Extravagant exaggeration of statement |
| Hypercritical | Overcritical |
| Hyperemia | Superabundance of blood |
| Hyperopia | Farsightedness |
| Hypersensitive | Excessively sensitive |
| Hypertrophy | Enlargement of a body part or organ, as from excessive use |
| Hypodermic | Injected under the skin |
| Hypothesis | Theory or supposition assumed as a basis for reasoning |
| Hypothetical | Assumed without proof |