Morphologists classify words into at least two categories: simple and complex. A simple word such as dog seems to be an irreducible unit: there seems to be no way to break it down further into meaningful parts. On the other hand, the word dogs seems to be made up of two parts: the noun dog and a plural ending (-s in this case). Not every noun in English forms its plural in this fashion, but many do. In linguistics these meaning-bearing parts of a complex word—that is, the different building blocks