Teacher: In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.
Teacher: Now, understand the problem? If you are still confused, see the following example:
The Inheritance Cycle is a series of fantasy books written by Christopher Paolini.
Solution: The Inheritance Cycle is a tetralogy of young adult high fantasy novels written by American author Christopher Paolini.
Reason: The output sentence elaborates on the input sentence without changing its general meaning e.g. "tetralogy of young adult high fantasy novels".

Now, solve this instance: When this is the case , traction is often expressed as the ratio of the maximum tractive force to the normal force and is termed the " coefficient of traction " ( similar to coefficient of friction ) .
Student:
Traction can also refer to the " maximum " tractive force between a body and a surface , as limited by available friction ; when this is the case , traction is often expressed as the ratio of the maximum tractive force to the normal force and is termed the " coefficient of traction " ( similar to coefficient of friction ) .