Let G be a finite abelian
group and let f : G → G be any function. Let rx: G → G be the function
rx(y) = x + y, x ∈ G. A study is made of conditions on f such that the semi-group
of functions generated by f and all rx under composition contains the zero function.
If G is cyclic, it is necessary and sufficient that f not be one-to-one. In general
some necessary conditions are given and a partial converse is given for these
conditions, which involve the behaviour of f on subgroups and cosets of
G.