(1889-1951) an Austrian philosopher. He studied in Britain under Bertrand Russell before World War I. After the war he moved back to Britain, becoming a British citizen in 1938. He worked on theories of language and philosophy. In his Tractatus Logico-Philosophicus (1922) he suggested the theory that language represents pictures of things according to established conventions (= general agreement). Later, he decided that this was wrong, and worked on the theory that usage (= the way words are used in a language) was more important.