This year's Reith Lecturer is Jean Aitchison, a Professor of Language and Communication in the Faculty of English Language and Literature at the University of Oxford and a Fellow of Worcester College, Oxford.

In her fourth lecture, Professor Jean Aitchison examines words themselves. An educated native speaker of English knows at least 50,000 words and word-learning ability is inbuilt in humans. Professor Aitchison explains how we manage to recall these words at speed when we need them, and how meaning and sound are interwoven.