occurring between vowels or voiced consonants. That led to many alternations: hūs ('house') vs. hūses ('of a house') ; wīf ('woman') vs. wīfes ('of a woman') . In Middle English, voiced allophones become phonemes, and they are solidly established in Modern English as separate phonemes by several sources: Borrowings from foreign languages, especially Latin, Ancient Greek, and Old French, which introduced sounds where they had not occurred: modern fine vs. vine (both borrowings from French); ether (from Greek) vs. either (native). Dialect mixture between Old English dialects (like Kentish) that voiced initial fricatives and the more standard dialects that did not. Compare fat vs. vat (both with f- in standard Old English) and fox vs. vixen (Old English fox vs. fyxen, from Proto-Germanic vs. ). Analogical changes that levelled former alternations: grass, grasses, grassy and glass, glasses, glassy with replacing the original between vowels (but to graze and to glaze, still with , originally derived from grass and glass, respectively). Contrast wife vs. wives; greasy, still with a in some dialects (such as that of Boston) and staff, with two plurals, analogical staffs and inherited staves. Loss of final , resulting in voiced fricatives at the end of a word where only voiceless fricatives had occurred. That is the source of the modern distinctions house vs. to house, teeth vs. to teethe, half vs. to halve. Reduction of double consonants to single consonants. That explains the contrast between kiss, to kiss (Old English coss, cyssan, with a double s) vs. house, to house with in the verb (Old English hūs, hūsian, with a single s). A Sandhi effect that introduced the voiced fricative /ð/ instead of original /θ/ at the beginning of unstressed function words. Contrast this with initial vs. thistle with initial . A sound change that caused fricatives to be voiced when preceded by a fully unstressed syllable. This change is reflected in the modern pronunciation of the endings spelt -s (the noun plural ending, the 'Saxon genitive' ending and the ending for 3rd person present indicative), which now have phonemic shape -, having developed in Middle English from - to - and then, after the deletion of the unstressed vowel, to - (e.g. halls, tells with from earlier halles, telles). The sound change also affects function words ending in original - that are normally unstressed. Contrast this with vs. is with ; off with vs. of with