However, some may find that Old English is a simpler and more coherent language since with it each letter specifically and invariably refers to a single sound. Unlike modern English there are no silent letters or phonetic inconsistencies to confuse them. Many of the words commonly used in English today have their roots in Old English. Words such as water, fort, house, earth and many others can be traced back to Old English. Furthermore, at some point in the 6th century, the Old English consonant cluster “sk” changed to “sk,” thereby changing the words “skield” to “shield.” This change affected all “sk” words existing in the language at that time. Therefore, any “sk” group in Modern English became part of the English language after the 6th century. Subsequently, around the 7th century, a change occurred in the pronunciation of vowels. With this the vowels began to be pronounced more in the front area of ​​the mouth. As a result, the plural of several nouns also began to have modified vowel pronunciation instead of changes in inflection. This has sometimes resulted in spelling revisions resulting in inconsistent pairings of modern English words, such as goose/geese, mouse/mice, or blood/bleeding, to name a few. Towards the end of the 8th century, Vikings from Scandinavia began raiding