Precoordinated expressions consist of a single concept identifier, followed optionally by any term that is associated with that concept. While the use of a term is not mandated, it is often preferable to include preferred term from an appropriate dialect within the expressions to improve the human-readability of the expression. For example: 73211009 | Diabetes mellitus| As mentioned, the syntax does not require a term to be used with each concept identifier, so the following is also a valid expression: 73211009 | diabetes mellitus|