 If an "m"-form formula_20 can be written with local coordinates
and
then formula_20 defines "symplectic structure".A "p"-form formula_24 is "stable" if it lies in an open orbit of the local formula_25 action where n=dim(M), namely if any small perturbation formula_26 can be undone by a local formula_25 action.So any "1"-form that don't vanish everywhere is stable; "2"-form (or "p"-form when "p" is even) stability is equivalent to nondegeneratacy.