a trait that is observed with higher frequency within the same family, whether
the etiology is genetic or environmental, or a combination of the two
Definition from: GeneReviews
from the University of Washington and the National Center for Biotechnology Information
- Tending to occur in more members of a family than expected by chance alone <a familial disorder>.
Definition from: Merriam-Webster's Medical Dictionary by Merriam-Webster Inc.
Related discussion in the Handbook
See also Understanding Medical Terminology.