Decalage

Decalage on a fixed-wing aircraft is the angle difference between the upper and lower wings of a biplane, i.e. the acute angle contained between the chords of the wings in question.

The decalage is said to be positive when the upper wing has a higher angle of incidence than the lower wing, and negative when higher wing's angle of incidence is lower than the angle of incidence of the lower wing. Positive decalage results in greater lift from the upper wing than the lower wing, the difference increasing with the amount of decalage.