It's like when you have a toy and you play with it all by yourself, that's called a monad. But when you have another friend to play with, that's called a dyad. In Greek philosophy, a dyad is when two things or ideas come together and interact with each other. It's like when you and your friend play together and share your toys, you can learn from each other and make new things that you couldn't do alone. So, in philosophy, a dyad is when two things or ideas come together and form a new way of thinking or understanding.