§2.def.1πᾶν παραλληλόγραμμον ὀρθογώνιον περιέχεσθαι λέγεται ὑπὸ δύο τῶν τὴν ὀρθὴν γωνίαν περιεχουσῶν εὐθειῶν.
Any right-angled parallelogram is said to be contained by the two straight lines containing the right angle.
§2.def.2παντὸς δὲ παραλληλογράμμου χωρίου τῶν περὶ τὴν διάμετρον αὐτοῦ παραλληλογράμμων ἓν ὁποιονοῦν σὺν τοῖς δυσὶ παραπληρώμασι γνώμων καλείσθω.
And in any parallelogramic area, let any one of the parallelograms about its diagonal together with the two complements be called a gnomon.