long vowels are shortened. are unrounded to , respectively. This occurred within the literary period. Some Old English dialects retained the rounded vowels, however. Early pre-cluster shortening: Vowels were shortened when falling immediately before either three consonances or the combination of two consonants and two additional syllables in the word. Thus, OE gāst > ModE ghost, but OE găstliċ > ModE ghastly (ā > ă) and OE crīst > ModE Christ, but OE crĭstesmæsse > ModE Christmas (ī > ĭ). Probably occurred in the seventh century as evidenced by eighth century Anglo-Saxon missionaries' translation into Old Low German, "Gospel" as Gotspel, lit. "God news" not expected *Guotspel, "Good news" due to gōdspell > gŏdspell. and were lowered to and between 800 and 900 AD. Initial became in late Old English. This occurred within the literary period, as evidenced by shifting patterns in alliterative verse. The Middle English Period This period is estimated to be c. 900–1400. Homorganic lengthening: Vowels were lengthened before , , , , probably also , , , when not followed by a third consonant or two consonants and two syllables. This probably occurred around AD 1000. Later on, many of these vowels were shortened again; but evidence from the Ormulum shows that this lengthening was once quite general. Remnants persist in the Modern English pronunciations of words such as child (but not children, since a third consonant follows), field (plus yield, wield, shield), old (but not alderman as it is followed by at least two syllables), climb, find (plus mind, kind, bind, etc.), long and strong (but not length and strength), fiend, found (plus hound, bound, etc.). Pre-cluster shortening: Vowels were shortened when followed by two or more consonants, except when lengthened as above. This occurred in two stages, the first stage occurring already in late Old English and affecting only vowels followed by three or more consonants, or two or more consonants when two syllables followed (an early form of trisyllabic laxing). Diphthong smoothing: Inherited height-harmonic diphthongs were monophthongized by the loss of the second component, with the length remaining the same. and initially became and . and initially became and . Middle English stressed vowel changes: (from Old English ) and became and , respectively. (from Old English ) and merged into . New front-rounded and (from Old English ) were unrounded to and . and were unrounded to and . became or ,