Which suffix would indicate an abnormal flow?

The suffix that indicates an abnormal flow is -rrhea. This suffix is derived from the Greek word "rhein," meaning "to flow." It is commonly used in medical terminology to describe various types of abnormal discharges or secretions, such as diarrhea (abnormal flow of feces) or rhinorrhea (abnormal flow of mucus from the nose).

In contrast, -phobia is a suffix referring to an irrational fear of something, -ation is typically used to denote a process or condition, and -ule refers to a small or diminutive structure. These other suffixes do not imply any type of flow, making -rrhea the appropriate choice for indicating an abnormal flow in medical terms.