'the writing system, which determines in a general way how written units connect with units of language. … the orthography–the system that actually implements the writing system' (Perfetti, 1999, 168)

'A "script" is just a set of distinct marks conventionally used to represent the written form of one or more languages… A "writing system" however is a script used to represent a particular language. … (Sproat 2000, 25)

'writing system A set of visible or tactile signs used to represent units of language in a systematic way…': [sense 1] 'the basic types of graphic systems designed to represent language…'; [sense 2]

'orthography Correct spelling and that part of grammar that deals with the rules of correct spelling' (Coulmas, 1996, 379)

'In the main 'writing system', 'script' and 'orthography' will be used interchangeably, though I shall tend to use 'writing system' when a script is cited as exemplifying a particular type of writing, and 'orthography' in connection with alternative conventions for using a given set of written marks' (Sampson, 1985, 20)