The best definitions are sometimes tautologies:
“A business capability is defined as the desired ability for the organisation to deliver a defined outcome, as referred to when defining the organisation’s strategy, or within a hierarchy of capabilities that can be traced to those used to define the organisation’s strategy. Importantly, if it’s not being referred to during the definition of strategy, it’s not a capability. Each capability must encapsulate multiple functions and may not reference any particular function except in the definition of it’s implementation. There is no need for a capability’s implementation to be defined for it to be a valid capability.”