From approximately 450 to 1100, England was the home of Old English. Though this language is the ancestor of the modern English that is spoken today, it differed from modern English in many ways. These included pronunciation, vocabulary and syntax.
Many of the differences in pronunciation were reflected in the vowel system. Unlike in modern English, Old English had a front high rounded vowel as in the French word "lune" (moon). The vowels were monophthongs, not diphthongs. Furthermore, Old English had a number of diphthongs which no longer occur in English such as "eo."
The consonants were similar but Old English had palatal and velar fricatives as in German. A word with a palatal fricative was "night" . Also, the interdental voiced fricative of "mother," the voiced labiodental fricative of "vest" and the voiced alveolar fricative of "zero" were allophones of their voiced counterparts and not phonemes as is the case today.
Much of the vocabulary of Old English was quite different from that of modern English. Here is a list to illustrate:
English: I, king, name, life, now, bread, tree, eye, lake, cheese
Old English: Ic, cyning, nama, lif, nu, hlaf, beam, eage, mere, ciese
The syntax of Old English was also different from that of modern English. Old English was a V2 language. This means that in sentences where the first word was not the subject of the sentence the second word had to be a verb. For example, in the sentence "Now we must go" Old English had to put "must" in second position. This resulted in the sentence "Now must we go" which is ungrammatical in modern English. Another difference was that inversion was used to generate questions with main verbs. The auxiliary "do" was not inserted. The question "Do you like fish?" was "Like you fish?" which is ungrammatical in modern English.
The ancestor of modern English is Old English, a language which differed significantly from the language of today. This is the reason that Old English texts are often translated. Without question, English has undergone many changes since its earliest days.