PDF: The Formation of Latin Stem Compounds This tutorial explains the general "rules" for the formation of what I refer to as Latin Stem Compounds -- compound words whose stems are made up of other Latin word stems. It also lists examples of compound words and the words used in their formation. Any comments and suggestions would be welcome. Note: Stem is used in the same way that it is used in Allen and Greenough's New Latin Grammar. So, for example, the stem of puella is puella-, not puell-.