= Rational section of a sheaf of modules
{title2=$\operatorname{Rat}(\mathcal F)=\varinjlim_{U\text{ dense open}}\Gamma(U,\mathcal F)$}
= Rational section
{synonym}
A rational section is a section on a dense <open subset>, with two representatives identified when they agree on a common dense <open subset>. Intersecting representatives' domains defines addition. Multiplication by a similarly represented <rational function on an algebraic variety> makes these classes a module over the ring $\operatorname{Rat}(X)$. For an <irreducible variety>, this ring is its <function field>.
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