Relating your services to your capabilities in SOA

So what exactly is a Service? If we are seeking a common definition of what SOA is (and much is made of the lack of this on the web), then we could at least start by defining the 'S' (in SOA).

There is some emerging consensus in some SOA communities that 'services are a way to gain access to, or make use, of a capability'.

What does this mean? Is it just semantics? Well actually it is important, and the reasons why are related to why services are a useful concept (and implicitly, when they're not!). I've posted a couple of thoughts as to why up on Nigel Green's Services Fabric blog.