An ordered set of DICOM Data Elements that define some real life object e.g. Image.

AKA DICOM Instance. Objects may be stored in files or transferred via network.

According to the standard, A DICOM Data Element (i.e. with a specific DICOM Tag) can appear only once in a DICOM object. To overcome this constraint , DICOM defines a special ‘sequence’ data type (Value Representation) that can hold a collection of DICOM Objects. This limitation may have contributed to the proliferation of DICOM Tags with similar meanings (but this is only a speculation).