Sentence:  <small>The use of the word ‘factor' shows the explicit intention of categorists to work with functions in an algebraic manner: a <WSD>category</WSD> is an algebra of functions.</small> 
Meaning of the word marked with <WSD> tags:  A collection of objects, together with a transitively closed collection of composable arrows between them, such that every object has an identity arrow, and such that arrow composition is associative.