What does $\Omega^\bullet(M)$ mean?

Question

What does $\Omega^\bullet(M)$ mean?

I know that $\Omega^k(M)$ is the set of all differential k-forms.

Thanks in advance!

Answer 1

$\Omega^\bullet(M) = \bigoplus_{k=0}^{\dim M} \Omega^k(M)$ is the space of all differential forms, which is $\mathbb Z$ graded by degree.