"bras bas [brah bah]: Positions of the arms. Although the positions of the feet are standard in all methods, the positions of the arms are not, each method having its own set of arm positions. The Cecchetti method has five standard positions with a derivative of the fourth position and two derivatives of the fifth position. The French School has a preparatory position and five standard positions. These positions are used in some Russian schools. The Russian School (Vaganova) has a preparatory position and three standard positions of the arms."
Ballet Dictionary - ABT: https://www.abt.org/explore/learn/ballet-dictionary/