ἐπιπρόσθησις
epiprosthēsis

Αἱ τοῦ ἡλίου ἐκλείψεις γίνονται κατ' ἐπιπρόσθησιν σελήνης. Μετεωρότερου γὰρ φερομένου τοῦ ἡλίου, ταπεινοτέρας δὲ τῆς σελήνης, ὅταν κατὰ τὴν αὐτὴν μοῖραν γένηται ὁ ἥλιος καὶ ἡ σελήνη, ὑποτροχάσασα ἡ σελήνη τῷ ἡλίῳ ἀντιφράττει ταῖς ἀπὸ τοῦ ἡλίου φερομέναις αὐγαῖς πρὸς ἡμᾶς.

‘Solar eclipses happen due to covering by the Moon. For since the Sun moves higher, and the Moon lower, whenever the Sun and the Moon arrive at the same degree, the Moon, having run under the Sun, blocks the rays moving from the Sun towards us.’

Διόπερ οὐδὲ ῥητέον αὐτὰς κυρίως ἐκλείψεις, ἀλλ’ ἐπιπροσθήσεις. Τοῦ μὲν γὰρ ἡλίου οὐδὲ ἕν μέρος οὐδέποτε ἐκλείψει· ἡμῖν δὲ ἀθεώρητος γίνεται διὰ τὴν ἐπιπρόσθησιν τῆς σελήνης.

‘And therefore, it should not be said that these [solar eclipses] are ‘failings’ in the proper sense, but rather ‘coverings’. For not one part of the Sun ever ‘fails’: it becomes invisible to us due to the covering by the Moon.’