The table below lists the major differences between fusion and fission reactions.
| Nuclear Fission | Nuclear Fusion |
| Nuclear fission is a nuclear reaction that splits a heavy atom into two or more smaller ones. | Nuclear fusion is a nuclear reaction that combines two or more small atoms to form a large atom. |
| It does not occur naturally. | The universe is full of instances of nuclear fusion reactions. Every star uses it to produce energy. |
| It produces a large quantity of energy. | It produces greater energy than the fission reaction. |
| Does not require a lot of energy to split an atom into two. | Requires a lot of heat and pressure for the process to happen. |