In philosophy, substance means, approximately, that element of an object without which it would not exist. In the millennia-old Aristotelian tradition[?], as well as early modern[?] traditions that follow it, substances are treated as having attributes[?] and modes[?].
... British Aerospace EAP prototype which had first flown in 1986, and culminating in the first flight of the Typhoon prototype in 1994 (then just known as the Eurofighter EF ...