What is the difference between synthesis and breakdown reactions?

A synthesis reaction is where two (or more) chemicals or elements combine to create one new product. A decomposition reaction is the opposite meaning it is when one compound is broken down into the 2 (or more) compounds/elements it is made up of. Both of these refer to compounds, not mixtures. Mixtures cannot have synthesis or decomposition reactions. The difference between a compound and a mixture is that a compound is chemically bonded together at the atomic level while a mixture is just mixed together.