Which prefix indicates a condition of being "Abnormally low"?

The prefix that indicates a condition of being "abnormally low" is "hypo-." This prefix comes from the Greek word "hypo," which means under, beneath, or less than. It is commonly used in medical terminology to describe a state or condition where something is lower than normal levels. For example, "hypoglycemia" refers to abnormally low blood sugar levels.

Other prefixes do not convey this specific meaning. "Hyper-" means excessive or above normal, typically indicating a condition of increased levels. "Normo-" refers to normal levels or conditions. "Oligo-" suggests a deficiency or low quantity but is often used in specific contexts, such as "oliguria," which refers to low urine output, rather than broadly indicating a general state of being low. Therefore, "hypo-" is the most appropriate prefix to indicate an abnormally low condition.