Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
nōnānus, a, um, adj. [nona, sc. legio], of or belonging to the ninth legion: miles nonanus, Tac. A. 1, 23.
Absol.: nōnānus, i, m., a soldier of the ninth legion, Tac. A. 1, 30; 14, 38.