arduus, a, um. adj. c. s.
高者。難者。 Ardua terrarum 諸山。Res arduae 災難。
Joaquim Affonso Gonçalves, Lexicon Magnum Latino-Sinicum, 3rd edition (Peking: Typis Congregationis Missionis, 1936 [1st ed. Macau, 1841]). Digitized at Dickinson College, 2023.