In this chapter, we will look at the three elements that form the basis of the theory of signification for Boethius, namely expressions, understanding and reality, and their relation to one another. Boethius did not write separate treatises on the philosophy of language, cognition or metaphysics. Instead, he wrote commentaries on Aristotelian logic. By the time he began to work on them around the start of the sixth century, the texts of Aristotelian logic were read in a fixed sequence: the first three were the Isagoge, Categories and On Interpretation, and Boethius treated topics as and when they are discussed in these texts by Porphyry and Aristotle. To grasp Boethius' theory of signification, we must therefore gather his views on utterances, understanding and reality from a variety of places in his commentaries and put them together. As evidenced by the sheer length of the treatment of Aristotle's brief comments on signification in his commentaries on On Interpretation, there is no question but that Boethius was aware of the importance of a theory of signification in explaining how the words we use are able to make sense to others and to refer to reality. We might expect, therefore, that Boethius' views on language broadly cohere with his theory of cognition and metaphysics given elsewhere in the commentaries on the Isagoge and Categories.