Here's why:
* Introduction of French words: The Norman conquerors brought with them their own language, Old French, which became the language of the court, government, and law. This led to the introduction of a vast number of French words into English, particularly in areas like government, law, religion, and food.
* Shift in grammar: Old English grammar was heavily inflected (meaning words changed form depending on their grammatical function). The influence of French led to a simplification of grammar, with fewer inflections and a greater reliance on word order.
* Changes in pronunciation: The Norman Conquest also contributed to changes in pronunciation, as the interaction between Old English and Old French speakers resulted in a gradual shift in sounds.
While the Norman Conquest marked the beginning of the Modern English period, it's important to note that the transition from Old English to Modern English was a gradual process that took several centuries. The language continued to evolve over time, absorbing words from other languages and undergoing further grammatical and phonetic shifts.