Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
rectĭo, ōnis, f. [rego], a leading, guiding, government, direction (Ciceronian): rerum publicarum, Cic. Fin. 5, 4, 11.
Plur.: rerum publicarum, Cic. Fin. 4, 22, 61 (Madv. conj. rerum publicarum rectionis genera).