If "η"("θ") = "θ", then the exponential family is said to be in "canonical form". By defining a transformed parameter "η" = "η"("θ"), it is always possible to convert an exponential family to canonical form. The canonical form is non-unique, since "η"("θ") can be multiplied by any nonzero constant, provided that "T"("x") is multiplied by that constant's reciprocal, or a constant "c" can be added to "η"("θ") and "h"("x") multiplied by formula_13 to offset it. In the special case that "η"("θ") = "θ" and "T"("x") = "x" then the family is called a natural exponential family.