ŏpācĭtas, ātis, f [opacus],
shadiness , shade (post-Aug.), Col. 8, 17; amoena, Plin. 6, 30, 35, § 197; noctium, id. 2, 11, 8, § 52: ramorum, id. 17, 1, 1, § 5: arborum, Tac. A. 11, 3.
opācitās ātis, f opacus, shadiness, shade : arborum, Ta. ...
An Elementary Latin Dictionary