hyp, hypo-Prefix denoting below, beneath, less than. Hypo- is the exact opposite of HYPER-. Reference to that entry will indicate the range of uses. Almost all the hyper- entities mentioned there have their hypo- counterparts. There is, however, one usage in which hypo- is commoner than hyper-. This is when it is used to refer to position in the body, as in hypochondrium or hypogastric. In this sense, the body is to be understood as standing upright, so hypo- indicates that the entity is nearer the soles of the feet than the part it qualifies. Hypo- is, however, also used in the sense of ‘deep to’ as in hypodermic. From the Greek hupo . Compare HYPER-.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005