There are many aspects of language that native English speakers take for granted. For example, there are words that look like they rhyme but don’t: come and home, and through and cough. This language loves tripping up anyone trying to learn it. It often befuddles its native speakers as well. They may say “o’clock” throughout their lives, but if they stop to think, they may wonder: What does the O stand for?
Quick Grammar Lesson: The punctuation mark known as the apostrophe has two common functions. The first demonstrates ownership using expressions like “children’s books” or “the director’s film”. It is also used in contractions to show that certain words or letters are missing.
Consider using “don’t” instead of “do not,” or “there’s” instead of “there is.” As a result, the apostrophe in o’clock implies that something was skipped, and many people have forgotten what it was.