Graphonomics is a big word that basically means the study of how people write! You know how you learn to write your letters and words in school? Well, scientists study how you write those letters and words and even your whole signature. They look at things like how you hold your pen or pencil, how fast or slow you write, and how much pressure you put on the paper.
Graphonomics can tell us a lot of interesting things about people. For example, if you write really fast and kind of messy, scientists might think that you're in a hurry a lot of the time. Or, if you make your letters really big and write with a lot of pressure, they might think that you're a strong and confident person.
Sometimes police and detectives will use graphonomics to try and figure out who wrote a certain note or letter. They can look at the way the letters are formed and compare it to samples of handwriting to try and match it up.
So, graphonomics is really just a fancy way of saying that scientists study how people write and what it can tell us about them. Cool, huh?