reciprocant

from The Century Dictionary.

• noun The contravariant expressing the condition of tangency between the primitive quantic and an adjoint linear form.
• noun A differential invariant; a function of partial differential coefficients of n variables connected by a single relation, this function being such that, if the variables are interchanged in cyclical order, it remains unchanged except for multiplication by some nth root of unity into some power of the same root of the continued product of the first differential coefficients of one of the variables relatively to all the others. For an example, see Schwartzian, n.