What is the difference between BHP (brake horsepower) and HP (horsepower)? So far as I know, brake horsepower (BHP) and horsepower (HP) are the same.  But some books tell me that the two concepts are totally different.  What is the difference between BHP and HP?
For machinery that involves power transmission via shafts and gears, they are the same- and the actual term is brake (not "break") horsepower, because the apparatus used to measure the horsepower output of a machine is called a brake dynamometer. 

For turbomachinery like jet engines where thrust is generated by movement of air, the concept of brake horsepower can't be applied- except in those cases where the turbine drives a propeller on a shaft. In these cases, the turbine's output shaft can be attached to a dynamometer and its horsepower output measured- and the result is quoted as shaft horsepower.