Lie

A lie was the action of telling something that was not the truth.

The Tenth Doctor occasionally lied. (TV: School Reunion, The Fires of Pompeii) He believed he did it to make himself feel better. (TV: Gridlock)

The Eleventh Doctor made a habit of lying, both to companions (TV: Flesh and Stone, The Lodger, The Impossible Astronaut, The Almost People, Let's Kill Hitler, The Wedding of River Song, The Name of the Doctor) and enemies. (TV: Victory of the Daleks, The Doctor's Wife, The Snowmen, Journey to the Centre of the TARDIS, Nightmare in Silver) This led River Song to declare "Rule One: The Doctor lies." (TV: The Big Bang, The Wedding of River Song) Eleventh Doctor even lied about his age, so much so that was unsure he was even lying about it when speaking to the War Doctor. (TV: The Day of the Doctor)

The Doctor would also lie about his name. In order to prevent him lying, the Time Lords constructed a Truth Field on Trenzalore to force him to speak truthfully. (TV: The Time of the Doctor)

According to, the Time Lords lied about the Doctor's origins, and that they were actually the Timeless Child. (TV: The Timeless Children)