Irene Roswitha Heim is a linguist and noted specialist in semantics. She was a professor at the
University of Texas at Austin and
UCLA before finally moving to the
Massachusetts Institute of Technology in 1989, where she is Professor of Linguistics and Head of the Linguistics Section of the Department of Linguistics and Philosophy. She is probably most famous for her 1982
University of Massachusetts dissertation "The semantics of definite and indefinite noun phrases" (ISBN 0-8240-5188-2), in which she argued (developing an insight by the philosopher
David Lewis) that indefinite noun phrases like
a cat in the sentence
If a cat is not in Athens, she is in Rhodes are not
quantifiers but free variables bound by an existential operator inserted in the sentence by a semantic operation that she dubbed
existential closure. She is also the co-author, with
Angelika Kratzer of one of the most influential textbooks of formal semantics (ISBN 0-631-19713-3), and is a co-editor (also with Angelika Kratzer) of the journal
Natural Language Semantics.