Concept

A concept is an abstract, universal idea, notion, or entity that serves to designate a category or class of entities, events, or relations. Concepts are abstract in that they omit the differences of the things in their extension, treating them as if they were identical. They are universal in that they apply equally to every thing in their extension. Concepts are also the basic elements of propositions, much the same way a word is the basic semantic element of a sentence.