sections and retractionsSectionsAndRetractions2009-01-06 18:11:322009-01-06 18:11:32Definitioncategoryretractionsectionretractablesectionablemorphismcategory theory% this is the default PlanetMath preamble. as your knowledge
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Let $f: A\rightarrow B$ is a morphism of a category.
\begin{itemize}
\item If there exists morphism $g: B\rightarrow A$ such that $g\circ f=1_A$ then $f$ is called \emph{retractable} and $g$ is called \emph{retraction} of $f$.
\item If there exists morphism $g: B\rightarrow A$ such that $f\circ g=1_B$ then $f$ is called \emph{sectionable} and $g$ is called \emph{section} of $f$.
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\section{References}
\begin{itemize}
\item \PMlinkexternal{Yet Another Text on general nonsense}{http://www.madore.org/~david/math/cat2.ps.gz}
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