A patronymic, or patronym, is a component of a personal name based on the name of one's father. A component of a name based on the name of one's mother is a matronymic, or matronym. Each is a means of conveying lineage.
In many areas patronymics predate the use of surnames. They, along with the less common matronymics, are still used in Iceland, where few people have surnames. For example, the son and daughter of Pétur Marteinsson would have different last names - Pétursson (for his son) and Pétursdóttir (for his daughter).
Many Irish, Scottish, Welsh, Spanish, Slavic, Manx, English, and Scandinavian surnames originate from patronymics, e.g. Wilson (son of William), Powell (ap Hywel), Fernández (of Fernando), Carlsson (son of Carl, e.g., Erik Carlsson), Milošević (son of Miloš, e.g., Slobodan Milošević). Similarly, other cultures which formerly used patronyms have since switched to the more widespread style of passing the father's last name to the children (and wife) as their own (as in Ethiopia).
Patronymics can simplify or complicate genealogical research. A father's first name is easily determinable when his children bear a patronymic; however, migration has frequently resulted in a switch from a patronymic to a surname due to different local customs. Depending on the countries concerned, family research in the nineteenth century or earlier needs to take this into account.
In biological taxonomy, a patronym is a specific epithet which is a Latinized surname. These often honor associates of the biologist who named the organism rather than the biologist himself. Examples include Gopherus agassizii, named by James Graham Cooper after Jean Louis Rodolphe Agassiz, and Acacia greggii, named by botanist Asa Gray after explorer Josiah Gregg.