a. Math. [f. L. contrā- against (CONTRA- 1) + -gredient: cf. COGREDIENT.] See quot.
1853. Sylvester, in Phil. Trans., CXLIII. I. 543. A system of variables is cogredient to another system when it is subject to undergo simultaneously therewith linear substitution of a like kind, and contragredient when it is subject to undergo linear substitution simultaneously therewith but of a contrary kind.
1880. Carr, Synops. Math., I. § 1813.
1885. Salmon, Higher Alg. (ed. 4), 120. Similarly the ray coordinates of different lines for the same system of reference are cogredient, but the axial coordinates are transformed by the inverse substitution, that is, are contragredient to the former.
