Middle English phonology is necessarily somewhat speculative, since it is preserved only as a written language. Nevertheless, there is a very large text corpus of Middle English. The dialects of Middle English vary greatly over both time and place, and in contrast with Old English and Modern English, spelling was usually phonetic rather than conventional. Words were generally spelled according to how they sounded to the person writing a text, rather than according to a formalised system that might not accurately represent the way the writer's dialect was pronounced, as Modern English is today. The Middle English speech of the city of London in the late 14th century (essentially, the speech of Geoffrey Chaucer) is used as the standard Middle English dialect in teaching and when specifying "the" grammar or phonology of Middle English. It is this form that is described below, unless otherwise indicated. In the rest of the article, abbreviations are used as follows: Sound inventory The surface sounds of Chaucerian Middle English (whether allophones or phonemes) are shown in the tables below. Consonants 1. The exact nature of Middle English r is unknown. It may have been an alveolar approximant , as in most Modern English accents, an alveolar tap or an alveolar trill . This article uses indiscriminately. Consonant allophones The sounds marked in parentheses in the table above are allophones: is an allophone of occurring before and For example, ring ('ring') is ; did not occur alone in Middle English, unlike in Modern English. are allophones of in coda position after front and back vowels, respectively. The evidence for the allophone after front vowels is indirect, as it is not indicated in the orthography. Nevertheless, there was historically a fronting of to and of * to [*] (and later, ) after front vowels in pre-Old English, which makes it very likely. Moreover, in late Middle English (post-Chaucer), sometimes became (tough, cough) but only after back vowels, never after front vowels. That is explained if the allophone is assumed to have sometimes become but that the allophone never did. For example, night ('night') is , and taught ('taught') is . (See H-loss, below.) Based on evidence from Old English and Modern English, and apparently had velarised allophones and or similar ones in some positions (perhaps all positions in the case of ). Voiced fricatives In Old English, , , were allophones of , , , respectively,