# 20. Cellular homology

In this lecture we define the homology $H_{ \bullet}(X, \mathcal{F})$ associated to a topological space $X$ with a *cell-like filtration*** **$\mathcal{F}$ and prove that this homology is the same as the singular homology of $X$.

In the special case where $X$ is a cell complex and $ \mathcal{F}$ arises from the skeleton filtration of $X$, we call this the *cellular homology* of $X$.

We conclude by giving an explicit formula for the boundary operator for a cell complex. This finally allows us to compute the homology of the real projective spaces, something that has eluded us so far.

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