cases of disyllabic laxing are due, as in southern and shadow above, to Middle English having had more unstressed sounds than Modern English: sutherne , schadowe . Cases such as please, pleasant and dine, dinner come from how French words were adapted into Middle English: a stressed French vowel was borrowed into English as an equivalent long vowel. However, if the stressed English vowel was originally an unstressed vowel in French, the vowel was not lengthened; an example of this which did not create an alteration is OF pitee → Middle English pite ; Old French plais- (stem of plaire) → Middle English plesen , plaisant → plesaunt . Some Latinate words, such as Saturn, have short vowels where from syllable structure one would expect a long vowel. Other cases differentiate British and American English, with more frequent disyllabic laxing in American English – compare RP and GA pronunciations of era, patent, primer (book), progress (noun) and lever, though there are exceptions such as leisure, yogurt, produce (noun), Tethys and zebra that have a short vowel in RP. On the other hand, American English is less likely to have trisyllabic laxing, for example in words such as privacy, dynasty, patronize and vitamin. Much of this irregularity is due to morphological leveling. Monosyllabic laxing Laxing also occurs in basic monosyllabic vocabulary, which presumably helps keep it active across generations. For example, the → shift occurs in the past-tense forms of basic verbs such as feel, keep, kneel, mean, sleep, sweep, weep and – without a suffix -t – in feed, read, lead. Other shifts occur in hide → hid, bite → bit, lose → lost, shoot → shot, go → gone, do → done, etc. References Sources Myers, Scott (1987). "Vowel Shortening in English". Natural Language & Linguistic Theory, Vol. 5, No. 4 (Dec., 1987), pp. 485–518. English phonology Vowel shifts