Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dĭācŏnātus, ūs, m. (and dĭācŏnī-um, i, n., Sever. Sulp. vita Mart. 5 al.) [diaconus], the office of deacon, deaconship, Hier. Ep. 22, 12 al.