A pre-coordinated term has a single code associated the term. A term may consist of one or more words. A well-defined collection of words represents a concept or thing.
For example, RadLex assigns the code RID1276 to the term left upper lobe bronchus.
A post-coordinated term has two or more codes that represent a collection of concatenated words. It concatenates preexisting terms to create a new concept. The concept is represented by a collection of concatenated codes ordered by when a word appears in the term.
For example, left and lung are concatenated words. Left lung is a term but the National Cancer Thesaurus assigns it two codes, C25229 and C12468.
