Question

What are redox reactions?

Answer 1

Redox reactions are reactions which involve formal electron transfer, and a change in oxidation state.

Explanation:

See this old answer, which includes directions to assign oxidation state, and also here for some more direction.

Note that redox reactions introduce electrons as formal reactants (or products) in a reaction. While this is a bit abstract it does seem to work. Note that for structural engineers oxidation of iron and steel structures is inevitable, and something to be prevented (and it's a losing battle!).