Have you ever heard a person talk in a different way than you do? Maybe they have an accent! An accent is when someone says words a little differently than you do because they come from a different place.
The people who lived in ancient Greece thousands of years ago also had accents! Even though they spoke the same language, they had different ways of saying the words. They had three different accents, which were like different musical notes or tones.
Imagine you have a toy piano with three different buttons that makes three different sounds. The ancient Greeks had a similar way of speaking with different buttons that they could press to create the different sounds.
Each accent had a special symbol that looked like a small mark over a letter. The ancient Greeks used these symbols to show which accent to use for each word.
So, just like you and I might sound a little different when we say certain words, the ancient Greeks had their own unique way of speaking too!