The period, comma, exclamation point, question mark, semicolon, and colon are the most common punctuation marks. These punctuation marks order and structure sentences. Without them, conversations would be difficult if not impossible. A period ends a sentence, but it can also indicate a pause or change of subject. A full stop is used instead to give a clearer separation between sentences. Some examples are "I love you" and "I love my life". No one word can replace the full stop because it serves another purpose too: it creates clarity by letting the reader know when one sentence ends and the next begins. A comma is a sign of omission. It allows the writer to expand on ideas within a sentence or provide additional information that doesn't relate directly to the topic at hand. Without the use of a comma, this sentence would be incomplete because it fails to include who Mary's classmates were. Using the comma makes the story more interesting because we get to learn about other students in Mary's class besides just her.