The phonetic properties of language are not entirely random. There are many repeated patterns and categories that give more abstract structure to the physical reality of the linguistic signal, both within a particular language and across languages. This chapter explores this abstract structure by looking at patterns in how the physical units of language can be combined, how they affect each other in patterned ways when they are combined, and the methods linguists can use to discover these patterns. When you’ve completed this chapter, you’ll be able to: