A programming technique where two or more functions are combined to create a new function, where the output of one function becomes the input of the next. It follows the mathematical concept (f ∘ g)(x) = f(g(x)).
From Latin 'componere' meaning to put together, borrowed from mathematical function composition developed in the 18th century. The programming concept emerged with functional languages in the 1950s-60s, emphasizing the mathematical foundation where complex operations are built by combining simpler functions.
Function composition is like building a factory assembly line where each station does one simple task perfectly - data flows from raw materials through each specialized function until you get the finished product! This is why Unix pipes are so powerful: 'cat file | grep error | sort | uniq' composes four simple functions into a complex data processing pipeline.
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