Old English phonology is necessarily somewhat speculative since Old English is preserved only as a written language. Nevertheless, there is a very large corpus of the language, and the orthography apparently indicates phonological alternations quite faithfully, so it is not difficult to draw certain conclusions about the nature of Old English phonology. Old English had a distinction between short and long (doubled) consonants, at least between vowels (as seen in sunne "sun" and sunu "son", stellan "to put" and stelan "to steal"), and a distinction between short vowels and long vowels in stressed syllables. It had a larger number of vowel qualities in stressed syllables – /i y u e o æ ɑ/ and in some dialects /ø/ – than in unstressed ones – /ɑ e u/. It had diphthongs that no longer exist in Modern English, which were /io̯ eo̯ æɑ̯/, with both short and long versions. The inventory of consonant surface sounds (whether allophones or phonemes) of Old English is as shown below. Allophones are enclosed in parentheses. The fricatives /f θ s/ had voiced allophones [v ð z], which occurred between vowels or a vowel and a voiced consonant when the preceding sound was stressed. stæf ('letter') /ˈstæf/: [ˈstæf] stafas ('letters') /ˈstɑfɑs/ > [ˈstɑvɑs] smiþ ('blacksmith') /smiθ/: [smiθ] smiþas ('blacksmiths') /ˈsmiθɑs/ > [ˈsmiðɑs] hūs ('house' noun) /ˈhuːs/: [ˈhuːs] hūsian ('to house') /ˈhuːsiɑn/ > [ˈhuːziɑn] forþ ('forth') /forθ/: [forθ] compare eorðe ('earth') /ˈeo̯rθe/ > [ˈeo̯rðe] fæþm ('fathom') /ˈfæθm/ > [ˈfæðm] Proto-Germanic (a fricative allophone of ) developed into the OE stop /d/, but Proto-Germanic (a fricative allophone of ) developed into the OE fricative /f/ (either its voiced allophone [v] or its voiceless allophone [f]). PG [ˈɸɑðɛːr] > OE fæder /ˈfæder/ PG [ˈstɑβɑz] > OE stæf /ˈstæf/ PG > OE habban, hæfde [ˈhɑbbɑn], [ˈhævde] '(to) have, had' Phonological history of Old English#Palatalization Old English had a fairly large set of dorsal (postalveolar, palatal, velar) and glottal consonants: [k, tʃ, ɡ, dʒ, ɣ, j, ʃ, x, ç, h].