Duo may refer to:
The duodecimal system (also known as base 12 or dozenal) is a positional notation numeral system using twelve as its base.
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds.
A duopoly (or twinstick, referring to "stick" as jargon for a radio tower) is a situation in television and radio broadcasting in which two or more stations in the same city or community share common ownership.
The duodenal switch (DS) procedure, also known as biliopancreatic diversion with duodenal switch (BPD-DS) or gastric reduction duodenal switch (GRDS), is a weight loss surgery procedure that is composed of a restrictive and a malabsorptive aspect.
Duodenal atresia, also known as duodenojejunal atresia, is the congenital absence or complete closure of a portion of the lumen of the duodenum.
The Cathedral of Barcellona Pozzo di Gotto or Duomo of Saint Sebastian or Duomo of Barcellona Pozzo di Gotto, exact full name Minor Basilica of Saint Sebastian, is in Piazza Duomo and the main façade faces in Roma Street.