Which root word means "fear"?

The root word that means "fear" is derived from the Greek term "phobos," which is represented in English by the prefix "phobia." This term is commonly used to identify various types of anxiety disorders, where an individual experiences intense fear or aversion towards specific situations, objects, or activities. For instance, "arachnophobia" refers to the fear of spiders and is formed by combining the root "phobia" with "arachno," meaning spider.

The other choices do not pertain to the meaning of "fear." "Pneumo" relates to air or lungs, often used in medical terms associated with respiratory conditions. "Poly" means many or much, typically used in terms like "polytheistic," which refers to the belief in many gods. "Retro" denotes something that is backward or in past times, such as in the term "retroactive." Thus, "phobia" stands out as the correct choice, unequivocally linking it to the concept of fear.