Carbon-14 can also be produced by other neutron reactions, including in particular Carbon-13|(n,γ) and Oxygen-17|(n,α) with thermal neutrons, and Nitrogen-15|(n,d) and Oxygen-16|(n,) with fast neutrons. The most notable routes for  production by thermal neutron irradiation of targets (e.g., in a nuclear reactor) are summarized in the table.
Carbon-14 may also be radiogenic (cluster decay of , , ). However, this origin is extremely rare.