[[!redirects propositional image]] ## Definition ## Given a function $f:A \to B$, we define the __propositional image__ of $f$ as $$\mathrm{im}(f) \coloneqq \sum_{y:B} \left[\mathrm{fiber}(f, y)\right]$$ ## See also ## * [[fiber]] * [[axiom of replacement]] * [[graded module]] ## References ## * Marc Bezem, Ulrik Buchholtz, Pierre Cagne, Bjørn Ian Dundas, and Daniel R. Grayson, [Symmetry book](https://unimath.github.io/SymmetryBook/book.pdf) (2021) category: not redirected to nlab yet