Popular debates about language frequently revolve around on-going or recent changes, and linguistic differences that emerge between communities. By contrast, linguistic theory often focuses on the knowledge that individual speakers have about a single variant of the language, without regard to how that grammar relates to the grammars of previous generations or other members of the community.

In this class, we will examine how language varation and change shape and are shaped by grammar. How does your version of English differ from the English of your friends? your classmates? your parents? Why is there so much variation even within a single community, and how does variation lead to change? Are changes "errors" or corruption of language? Do changes optimize, or improve language? Does grammar play a role in shaping and constraining language change? How is linguistic variability used to construct or convey social identity?

We will tackle these questions, using large scale data sets to explore the linguistic variation and change that surrounds us every day. Along the way, we will examine approaches to quantifying, formalizing, and explaining the ways in which linguistic systems vary across space and time. The course involves a series of in-depth case studies that provide insight into the mechanisms that create and constrain change. We will focus first on "unintentional" sources of change, such as changes in the type or amount of data that are available to language learners. Next, we will ask whether there are "intentional" types of change that are used to accomplish a purpose: signaling community and group membership, eliminating dispreferred linguistic structures, etc. A recurring theme will be the ways in which different grammatical systems co-exist in a single speech community, and how grammar constrains variation and change. In order to understand this, we will need to simultaneously consider the grammatical analysis of the language of individual speakers, alongside quantitative data drawn from the historical record and present-day speech communities.