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.

Let me give you an example: The Inheritance Cycle is a series of fantasy books written by Christopher Paolini.
The answer to this example can be: The Inheritance Cycle is a tetralogy of young adult high fantasy novels written by American author Christopher Paolini.
Here is why: The output sentence elaborates on the input sentence without changing its general meaning e.g. "tetralogy of young adult high fantasy novels".

OK. solve this:
Two common ways of writing it are sa / vol or SA : V. Either of these say to divide the surface area by the volume .
Answer:
The surface-area-to-volume ratio , also called the surface-to-volume ratio and variously denoted sa / vol or SA : V , is the amount of surface area per unit volume of an object or collection of objects .