I read some patents, it seems they were divided from a single application as the detailed descriptions are the same.
The question is, when an application is divided into multiple applications because the lack of unity of invention, do they must retain the same description as the original application? Or they can add or remove some parts?
My feeling says they must have the same description, as adding or removing any material may change the scope of the invention, but I am not sure. For example, because the lack of unity, the divisional application can remove the part that unrelated to the invention, is it acceptable?
If they must retain the same description, then what make them different? Is that they are only different in claims?