A sub-specialization (German: "Schwerpunkt", literally: focus) is described as a further specialization within the field, which is based on the specialist qualification. That means a sub-specialization can only be acquired after completion of a specialist postgraduate qualification.

What does sub specialize mean?

: to concentrate one's efforts in a special occupation, practice, or field of study that is part of a broader specialty : to practice or study within a subspecialty Like most surgical specialists, neurosurgeons subspecialize in different areas, such as tumors, cerebrovascular, seizure, pituitary gland and pain surgery. ...

What is the mean of specializing?

1 : to concentrate one's efforts in a special activity or field : become or be a specialist specialize in anesthesiology. 2 : to undergo evolutionary specialization.