Everything in ballet is said in French. All of the jumps, all of the turns, all of the positions, everything. Ballet itself is actually a French word that the Americans use. Ballet was originally started in a France so that is why everything is in French. In most intermediate or advanced ballet classes teachers want you be able to translate every move and be able to spell them. It is especially hard to spell the moves because it is a different language. The great thing about it is the translation for the French word usually describes the move or position. For example glissade means to glide and the movement is gliding across the floor. Unfortunately some translations make no since what so ever. An example of that is pas de chat means jump of the cat.
Here is a link to a ballet dictionary:
American Ballet Theatre-Ballet Dictionary