A number that identifies a specific DICOM Data Element and defines the data element name, content and data type.

The tag is a long number (4 bytes) comprised of two short numbers (2 bytes each), group and element. Related tags usually share the same group, for example patient data elements belong to group 10.

Tags are usually written as a pair of two 4 hexadecimal digits in the following form: (gggg,eeee).