This chapter discusses medical prefixes and their meanings. It provides a table listing 50 common prefixes used in medical terminology and their definitions. Examples include "a-" meaning "without", "intra-" meaning "within", and "hyper-" meaning "excessive". The chapter goals are to define basic medical prefixes, analyze how prefixes are combined with other word elements to form medical terms, and use the Rh condition as an example of an antigen-antibody reaction.