| Term | Definition |
| hyperactidity | excessive acidity, especially in the stomach |
| hyperactive | excessively active |
| hypercitical | excessively fault-finding: captious |
| hypersensitive | abnormally sensitive |
| hypertension | abnormally high blood pressure |
| hypodermic | small syringe with a hollow needle for making injections beneath the skin |
| hypoglycemic | afflitcted with hypoglycemia (an abnormally low concentration of sugar in the blood) |
| hyposensitize | make less sensitive |
| hypotension | abnormally low blood pressure |
| hypothermia | subnormal body temperature |
| subaqueous | underwater |
| subcutaneous | being, living, or introduced beneath the skin |
| sublethal | not quite lethal, insufficient to cause death |
| submarginal | below minimum standards, inadiquate for some end, unprotective |
| subservient | useful in an "under" or subordinate capacity, excessively submissive |
| supererogatory | beyond the requirements of duty, performed to an extent not demanded |
| superficial | over or on the surface only, not frofound or thorough |
| supernatural | beyond what is natural or observable, not explainable by the laws of nature |
| supernumeracy | exceeding the standard or perscribed number, extra |
| supersonic | having a speed beyond that of sound |