By a different process, laxing is also found in disyllabic and monosyllabic words, for example, shade vs shadow, lose vs lost.
As a result of the changes, the pairs of vowels related by trisyllabic laxing often bear little resemblance to one another in Modern English; however, originally they always bore a consistent relationship.
Other cases differentiate British and American English, with more frequent disyllabic laxing in American English – compare RP and GA pronunciations of era, lever, patent, primer (book) and progress (noun), though there are exceptions such as leisure, produce (noun), Tethys, yogurt 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 dynasty, patronize, privacy and vitamin.
For example, the /iː/ → /ɛ/ 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, lead, read.