useage of the term "field" in QFT Wikipedia defines a field as "a physical quantity associated with each point of spacetime". So contrary to a particle, where physical quantities are associated with properties like position or momentum, the field itself is a physical quantity. (This definition restricts us to measureable fields like the em field but this is not important for my issue.) In ordinary QM, we talk about states of particles and observables which correspond to physical quantities. So if fields are physical quantities, they need to correspond to observables in QFT, which they do. But the states of what are we then looking at? The states of fields also. So QFT seems to use the term "field" in two distinct meanings: 1) Fields as physical systems which have no classical counterpart 2) Field operators which correspond to the classical fields This seems confusing to me. Have you also thought about this and have comments?