French was a language that originated in France. "Allons-y!", a catchphrase of the Tenth Doctor, was French for "let's go!" (TV: Midnight)
Susan Foreman studied French at Coal Hill School. Her teacher, Mademoiselle Quelou, said that Susan's French sounded like it came out of the Middle Ages. Susan confused French with Latin. (PROSE: Time and Relative)
Liz Shaw could speak French to at least a reasonable level of proficiency. (TV: The Ambassadors of Death)
Mickey Smith was surprised to find that the TARDIS' translation circuit also translated French. (TV: The Girl in the Fireplace)
While on a planet controlled by the War Lords, the TARDIS translation circuit did not translate French. (TV: The War Games) At another time, the translation circuit did not translate posters written in French. (TV: Vincent and the Doctor)
The Eighth Doctor spoke French to Fitz Kreiner, who was affecting a French accent, saying "On peut apprendre d'un grand homme meme lorqu'il se tait". (PROSE: The Taint)
- This phrase translates to English as "There is something to be learned from a great man even when he is silent."
The Eighth Doctor's companion Anji Kapoor spoke French. (PROSE: Escape Velocity)
"Le Mur" was French for "Wall". The Seventh Doctor explained this after Chief Inspector Patrick Mullen misnamed Le Mur Engineering as "Lemur Engineering", which the Doctor thought was an odd name for an English company. "Le Mur" made more sense, given the presence of a Mr Wall. (PROSE: Illegal Alien)
Luke Smith spoke French perfectly. He told Clyde Langer in French that the had devided his forces on a video game about the battle of Waterloo. Clyde however, couldn't understand it. (PROSE: The Last Sontaran)