There are four types of weakness abstractions: Pillar, Class, Base, and Variant.
CWE Abstraction
These abstraction types correlate with the amount of specific information in the CWE. This specific information includes dimensions such as behavior, property, resource, coding language, and technology. A set of weaknesses can be grouped into a Category, which is simply a collection of similar weaknesses that share common characteristics, but not the same combination of the dimensions above.
For root cause mapping, CWEs at the Base and Variant level should be used whenever possible to ensure providing adequate specificity, actionability, and root cause information for a vulnerability. Class level CWEs may be used for root cause mapping if there is no accurate Base or Variant level CWE.