circumstances. A similar palatalization happened in Frisian, but by this point the languages had split up; the Old English palatalization must be ordered after Old-English-specific changes such as a-restoration. Generally, the velar stops were palatalized before or ; after when not before a vowel; and was palatalized at the beginning of a word before front vowels. (At this point, there was no word-initial .) was palatalized in somewhat broader circumstances: By any following front vowel, as well as by a preceding front vowel when a vowel did not immediately follow the . later becomes , but not before the loss of older below. is palatalized in almost all circumstances. PG > ModE ship (cf. skipper < Dutch schipper, where no such change happened), but West Frisian skip. PG > OE scyrte > ModE shirt, but > ON skyrt > ModE skirt. An example of retained is PG > OE ascian > ModE ask; there is evidence that OE ascian was sometimes rendered metathetized to acsian, which is the presumed origin of ModE ask. Palatal diphthongization: Initial palatal , , trigger spelling changes of a > ea, e > ie. It is disputed whether this represents an actual sound change or merely a spelling convention indicating the palatal nature of the preceding consonant (written g, c, sc were ambiguous in OE as to palatal , , and velar or , , , respectively). Similar changes of o > eo, u > eo are generally recognized to be merely a spelling convention. Hence WG > OE geong > ModE "young"; if geong literally indicated an diphthong, the modern result would be *yeng. It is disputed whether there is Middle English evidence of the reality of this change in Old English. i-mutation: The most important change in the Old English period. All back vowels were fronted before a in the next syllable, and front vowels were raised. > (but > before or ); > > ; > ; , > > ; this also applied to the equivalent short diphthongs. Short > by an earlier pan-Germanic change under the same circumstances; often conflated with this change. This had dramatic effects in inflectional and derivational morphology, e.g. in noun paradigms (fōt "foot", pl. fēt "feet"); verb paradigms (bacan "to bake", bæcþ "he bakes"); nominal derivatives from adjectives (strang "strong", strengþ(u) "strength"), from verbs (cuman "to come", cyme "coming"), and from other nouns (fox "fox",