Function Description Defects:
Features may be described as distinguishing characteristics of a software component or a system.
Features refer to functional aspects of the software that map to functional requirements as described by the user and clients.
Features that also describe the quality requirements such as performance and reliability.
Feature defects are due to the feature description.
If we fail to specify the description of a specific feature the developer may not understand it properly due to this we may get the undesired behavior of the software.