Capital letters essentially have three functions: to mark the beginning of a sentence, to indicate titles and to distinguish proper nouns from other words. It is impossible to establish absolute rules for all aspects of capitalisation because it often depends on the role of a word in a sentence, the writer’s personal taste or the house style being followed. It is largely the second and third functions mentioned above – titles, and the distinction between proper nouns and other words – that lead to discrepancies in practice: authors can apply traditional or more modern approaches to title capitalisation (that is to say, maximal and minimal capitalisation, respectively), and sometimes there are differences of opinion over exactly what constitutes a proper noun and how words derived from proper nouns should be dealt with. Whatever decisions are taken, however, writers should strive to maintain consistency.