Therefore, it may be said that "He studies medicine" but not that "He reads medicine". When referring to time, Australians will refer to 10:30 as half past ten and do not use the British half ten. Similarly, a quarter to ten is used for 9:45 rather than (a) quarter of ten, which is sometimes found in American English. Australian English does not share the British English meaning of sat to include sitting or seated. Therefore, uses such as I've been sat here for an hour are not encountered in Australian English. To have a shower or have a bath are the most common usages in Australian English, in contrast to American English which uses take a shower and take a bath. The past participle of saw is sawn (e.g. sawn-off shotgun) in Australian English, in contrast to the American English sawed. The verb visit is transitive in Australian English. Where the object is a person or people, American English also uses visit with, which is not found in Australian English. An outdoor event which is cancelled due to inclement weather is rained out in Australian English. This is in contrast to British English where it is said to be rained off. In informal speech, sentence-final but may be used, e.g. "I don't want to go but" in place of "But I don't want to go". This is also found in Scottish English. In informal speech, the discourse markers yeah no (or yeah nah) and no yeah (or nah yeah) may be used to mean "no" and "yes" respectively. Spelling and style As in all English-speaking countries, there is no central authority that prescribes official usage with respect to matters of spelling, grammar, punctuation or style. Spelling There are several dictionaries of Australian English which adopt a descriptive approach. The Macquarie Dictionary is most commonly used by universities, governments and courts as the standard for Australian English spelling. The Australian Oxford Dictionary is another commonly-used dictionary of Australian English. Australian spelling is significantly closer to British than American spelling, as it did not adopt the systematic reforms promulgated in Noah Webster's 1828 Dictionary. Notwithstanding, the Macquarie Dictionary often lists most American spellings as acceptable secondary variants. The minor systematic differences which occur between Australian and American spelling are summarised below: French-derived words which in American English end with or, such as color, honor, behavior and labor, are spelt with our in