Is there a term for the difference between the angle of incidence of the
wing and the angle of incidence of the tailplane? I have heard/read
decalage used this way; however, wikipedia says decalage means the
difference between the angles of incidence between the two wings of a
bi-plane. (Thinking of that makes me think that extending Fowler flaps
turns the aircraft into a bi-plane).

Is there a separate term? Is this usage correct (Is Wikipedia just
incomplete?)?