Biologists reckon that most species that have ever existed are extinct. That is true of words, too. Of the Oxford English Dictionary’s 231,000 entries, at least a fifth are obsolete. They range from “aa”, a stream or waterway (try that in Scrabble), to “zymome”, “that constituent of gluten which is insoluble in alcohol”.
Obscene language presents problems, the linguist Michael Adams writes in his new book, In Praise of Profanity, “but no one seems to spend much time thinking about the good it does.” Actually, a lot of people in the last few decades have been considering its benefits, together with its history, its neuroanatomy, and above all its fantastically large and colourful word list.