In spite of a quite reasonable definition of capability provided by the Joint Staff, confusion around the meaning and use of this term abounds in the DoD systems engineering and architecture communities. This paper reviews the Joint Staff\’s authoritative definition of capability and available definitions for this definition\’s constitutive terms. Based upon models prepared for the Air Force enterprise architecture program, the paper then presents an architectural pattern that faithfully represents the meaning intended by the authoritative definition. The paper describes how this pattern relates to the semantics of the DoDAF 2.0 meta-model (DM2). Using this pattern, the paper then suggests a vocabulary that may be used to discuss capabilities; this vocabulary can mediate differences between DoDAF and MoDAF uses of the term capability. The paper identifies some issues that are raised by this model-based approach to understanding capabilities and suggests topics, such as red team architectures, for further study.