Definition 70.17.1. Let $k$ be a field. Let $X$ be a proper algebraic over $k$. Let $\mathcal{F}$ be a coherent $\mathcal{O}_ X$-module. In this situation the *Euler characteristic of $\mathcal{F}$* is the integer

\[ \chi (X, \mathcal{F}) = \sum \nolimits _ i (-1)^ i \dim _ k H^ i(X, \mathcal{F}). \]

For justification of the formula see below.

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