Back in the spring of 2022, professor of linguistics David Pesetsky was talking to an undergraduate class about relative clauses, which add information to sentences. For instance: "The senator, with whom we were speaking, is a policy expert." Relative clauses often feature "who," "which," "that," and so on.

As Evile and Pesetsky show in a newly published paper, “whom of which” obeys very specific rules, whose nature contributes to a larger discussion about sentence construction. The paper, “Wh-which relatives and the existence of pied piping,” appears this month in the journal Glossa.

“It seems to be brand new, and it’s very colloquial, but it’s extremely law-governed,” says Pesetsky, the Ferrari P. Ward Professor of Modern Languages and Linguistics at MIT.