A divisional application is the dividing of an application into two or more applications. A divisional application is filed when a complete application for an invention has already been filed and you wish to have some of the specification matter in the application covered by a separate patent. The situation typically arises during the examination process if the Commissioner reports that the application is for more than one invention. Divisional applications may retain the priority date of the original application. There are certain time limits within which such divisional applications may be made as well as restrictions on the scope of what can be claimed in relation to the parent specification.
a later application for an independent or distinct invention disclosing and claiming (only a portion of and) only subject matter disclosed in the earlier or parent application
a separate patent application carved out of a prior pending application and discloses and claims only subject matter originally claimed in the prior application
an application during the pendency of a prior application continuing the same disclosure but with claims directed to an invention that differs from the original application; usually filed in response to a Restriction Requirement from the PTO.
If an inventor initially tries to patent an invention that is actually two or more separate inventions, he or she will be required to cut out some of the claims from the original patent application.