A one-name study is a project researching a specific surname, as opposed to a particular pedigree (ancestors of one person) or descendancy (descendants of one person or couple). Some people who research a specific surname may restrict their research geographically and chronologically, perhaps to one country and time period, while others may collect all occurrences world-wide for all time. A one-name study is not limited to persons who are related biologically. Studies may have a number of family trees which have no link with each other.