  A hyperplane arrangement is called formal provided all linear dependencies
among the defining forms of the hyperplanes are generated by ones corresponding
to intersections of codimension two. The significance of this notion stems from
the fact that complex arrangements with aspherical complements are formal. The
aim of this note is twofold. While work of Yuzvinsky shows that formality is
not combinatorial, in our first main theorem we prove that the combinatorial
property of niceness of arrangements does entail formality. Our second main
theorem shows that formality is hereditary, i.e. is passed to restrictions.
This is rather counter-intuitive, as in contrast the known sufficient
conditions for formality, i.e. asphericity, freeness and niceness (owed to our
first theorem), are not hereditary themselves. We also demonstrate that the
stronger property of $k$-formality, due to Brandt and Terao, is not hereditary.
