Commutative diagram
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Given a number of functions, a commutative diagram shows that in many cases, applying different functions, perhaps in a different order gives the same result;
![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/22/Morphism.svg/220px-Morphism.svg.png)
Functions can be chained, Mathematician talk about composing them:
![](http://upload.wikimedia.org/wikipedia/commons/thumb/4/41/Morphism-Composition.svg/220px-Morphism-Composition.svg.png)
That way, it is possible to create a new function, which first applies f, then g, and call it h
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/01/Morphism-Composition-with-name.svg/220px-Morphism-Composition-with-name.svg.png)
But h can of course be any other path as well. A diagram is called commutative diagram, if it doesn't matter what path is chosen to get from A to C.