Where does a period always appear in written English?

A period is used in written English to signify the end of a sentence, indicating that a complete thought has been expressed. This punctuation mark is essential for clarity and readability, helping the reader to identify where one statement concludes and another may begin.

In contrast, a period does not appear in the middle of a sentence because its function is to denote the cessation of a complete idea, rather than to separate phrases. Similarly, it is not placed at the beginning of a sentence as this would confuse the reader about where the sentence starts. Lastly, while a period can signal the end of a paragraph, it does not serve the same function; paragraphs may end with various structures that don't necessarily include a period if they are continuing into another thought or idea. Consequently, the correct location for a period, ensuring proper grammatical structure, is clearly at the end of a sentence.