hypo

"Hypo" usually means "under," "below normal," or "too little." Most often, you'll see it as a prefix in medical or scientific words. For example, hypothermia means body temperature that is too low, and hypotension means blood pressure that is below normal. In everyday speech, especially in British English, a hypo can also mean a hypoglycemic episode, when someone's blood sugar drops too low.

The word "hypo" comes from Greek and basically means "under" or "below." In English, it is used most often as a prefix in medical, scientific, and technical words to show that something is under, lower than normal, or not enough.

You will often meet it in health terms. Hypoglycemia means low blood sugar. Hypotension means low blood pressure. Hypothermia means body temperature that has fallen dangerously low. In all of these, "hypo" tells you that the level is below what is normal or healthy. It can also mean physically under something, as in hypodermic, which literally means "under the skin."

Outside those examples, the idea stays much the same: something is lower, less, or underneath. In common use, hypoallergenic describes something that is less likely to cause an allergic reaction. The exact meaning can shift a little from word to word, but the general sense of "under" or "too little" usually remains.

As a word on its own, hypo can also be a shortened form. In British English, it often means a hypoglycemic attack or episode. In some contexts, especially older ones, it can also mean a hypodermic injection or needle. So when you see or hear "hypo," the main idea is usually that something is under, lower than normal, or reduced.