Answer: Fission is the splitting of a nucleus when it is bombarded by neutrons.
Explanation:-
Nuclear fusion is a process which involves the conversion of two small nuclei to form a heavy nuclei along with release of energy.
\(_{94}^{239}\textrm{Pu}+_2^4\textrm{He}\rightarrow _{96}^{242}Y+_0^\textrm{n}\)
Nuclear fission is a process which involves the conversion of a heavier nuclei into two or more small and stable nuclei along with the release of energy.
\(_{92}^{235}\textrm{U}+_0^1\textrm{n}\rightarrow _{56}^{143}Ba+_{36}^{90}Kr+3_0^1\textrm{n}\)