δύσις

Ἡμέρα λέγεται διχῶς, καθ’ ἕνα μὲν τρόπον χρόνος ὁ ἀπ’ ἀνατολῆς ἡλίου μέχρι δύσεως, καθ’ ἕτερον δὲ τρόπον ἡμέρα λέγεται χρόνος ὁ ἀφ’ ἡλίου ἀνατολῆς μέχρις ἡλίου ἀνατολῆς.

‘A day is spoken of in two ways, on the one hand as the time from sunrise till sunset, but on the other hand a day is spoken of as the time from sunrise till sunrise.’

often as compound ἡλίου δύσις (setting of the sun)

Οἰκοῦσι δ᾽ οὗτοι πρὸς βορέαν τοῦ Σκόμβρου ὄρους καὶ παρήκουσι πρὸς ἡλίου δύσιν μέχρι τοῦ Ὀσκίου ποταμοῦ.

‘And they (i.e. the Treres and Tilataeans) live to the north of the mountain Skombros and they have come along to the west as far as the river Oskios.’

Εἰ δέ γε ἀπὸ τῆς ἀνατολῆς ἐπὶ τὴν δύσιν ἐφέρετο ὁ ἥλιος, ἀεὶ τοὺς προανατέλλοντας ἀστέρας ἀθεωρήτους ἂν εἶναι συνέβαινεν· (...)

‘But if the sun would be moving from the east to the west, it would follow that the stars rising slightly earlier would always be unperceivable; (...)’