Typically, the subject will be represented using keywords, key phrases, or classification codes. Recommended best practice is to use a controlled vocabulary. (en)
A [second property](/specifications/dublin-core/dcmi-terms/#http://purl.org/dc/terms/subject) with the same name as this property has been declared in the [dcterms: namespace](http://purl.org/dc/terms/). See the Introduction to the document [DCMI Metadata Terms](/specifications/dublin-core/dcmi-terms/) for an explanation. (en)