opācus

1. Obscurum (σκοτερόν) denotes darkness as an obstruction of light, like σκότος in opp. to illustre. Auct. ad Her. iii. 19, 32. Plin. Pan. 69; whereas tenebræ (δνοφεραί) as the absence of light,) like ζόφος, κνέφας,) in opp. to lux. Cic. Ep. ad Q. Fr. i. 2; lastly, caligo (from celare) as the positive opposite to light and brightness, like ἀχλύς. Caligo denotes a greater degree of darkness than tenebræ; tenebræ than obscuritas; obscuritas than opacum and umbrosum. Cic. Acad. iv. 23, 72. Sensus quidem non obscuros facit sed tenebricosos. Plin. Ep. vii. 21. Cubicula obductis velis opaca, nec tamen obscura facio. Tac. H. ii. 32. Senatum et populum nunquam obscurari nomina, etsi aliquando obumbrentur. Hence, figuratively, obscurus denotes only an insignificant person, of whom nobody takes notice; whereas tenebricosus something positively bad, which seeks darkness that it may remain unobserved. 2. Opacus denotes shady, with reference to a pleasant and beneficial coolness, in opp. to apertus and apricus, like εὔσκιος; whereas umbrosus (umbra, ἀμαυρός,) implies a depth of shade approaching to darkness, like σκιόεις. (iii. 168.)