What is "liar!"

"Liar!" is a science fiction short story by American writer Isaac Asimov. It first appeared in the May 1941 issue of Astounding Science Fiction and was reprinted in the collections I, Robot (1950) and The Complete Robot (1982). It was Asimov's third published positronic robot story. Although the word "robot" was introduced to the public by Czech writer Karel Čapek in his 1920 play R.U.R. (Rossum's Universal Robots), Asimov's story "Liar!" contains the first recorded use of the word " robotics" according to the Oxford English Dictionary. In 1969 "Liar" was adapted into an episode of the British television series Out of the Unknown, although only a few short clips of this episode are known to exist. The events of this short story are also mentioned in the novel The Robots of Dawn written by the same author.