other non-native speakers of English from Scotland and Wales. The first of the Australian gold rushes in the 1850s began a large wave of immigration, during which about two percent of the population of the United Kingdom emigrated to the colonies of New South Wales and Victoria. The Gold Rushes brought immigrants and linguistic influences from many parts of the world. An example was the introduction of vocabulary from American English, including some terms later considered to be typically Australian, such as bushwhacker and squatter. This American influence was continued with the popularity of American films from the early 20th century and the influx of American military personnel during World War II; seen in the enduring persistence of such universally-accepted terms as okay and guys. The publication of Edward Ellis Morris's Austral English: A Dictionary Of Australasian Words, Phrases And Usages in 1898, which extensively catalogued Australian English vocabulary, started a wave of academic interest and codification during the 20th century which resulted in Australian English becoming established as an endonormative variety with its own internal norms and standards. This culminated in publications such as the 1981 first edition of the Macquarie Dictionary, a major English language dictionary based on Australian usage, and the 1988 first edition of The Australian National Dictionary, a historical dictionary documenting the history of Australian English vocabulary and idiom. Phonology and pronunciation The most obvious way in which Australian English is distinctive from other varieties of English is through its unique pronunciation. It shares most similarity with New Zealand English. Like most dialects of English, it is distinguished primarily by the phonetic quality of its vowels. Vowels The vowels of Australian English can be divided according to length. The long vowels, which include monophthongs and diphthongs, mostly correspond to the tense vowels used in analyses of Received Pronunciation (RP) as well as its centring diphthongs. The short vowels, consisting only of monophthongs, correspond to the RP lax vowels. There exist pairs of long and short vowels with overlapping vowel quality giving Australian English phonemic length distinction, which is also present in some regional south-eastern dialects of the UK and eastern seaboard dialects in the US. An example of this feature is the distinction between ferry and fairy . As with New Zealand English and General American English, the weak-vowel merger is complete in Australian English: unstressed is merged into (schwa), unless it is followed by