Almost symplectic manifold

In differential geometry, an almost symplectic structure on a differentiable manifold $$M$$ is a two-form $$\omega$$ on $$M$$ that is everywhere non-singular. If in addition $$\omega$$ is closed then it is a symplectic form.

An almost symplectic manifold is an Sp-structure; requiring $$\omega$$ to be closed is an integrability condition.