hyper- or hypo-? These two prefixes are easily confused. Hyper- means ‘excessively’ or ‘higher than normal’: hypercritical, hypersensitive, hyperinflation; hypertension is abnormally high blood pressure. Hypo- means ‘below’ or ‘less than normal’: a hypodermic needle pierces beneath the skin, hypotension is abnormally low blood pressure. Note that someone who is exposed to extreme cold suffers from hypothermia. The word hyperthermia also exists, but refers to a condition in which the body temperature is abnormally high