A septum (Latin: something that encloses; plural Septa) is a partition separating two cavities or spaces. Examples include:
- Nasal Septum: the cartilage wall separating the nostrils of the human nose.Often deviated or perforated through physical injury or cocaine abuse.
- Cephalopod Septa: walls between each chamber, or siphuncle, in shells of nautiloids, ammonites, and belemnites; i.e. cephalopods that retain an external shell.
- The wall dividing the right side of the heart from the left side.
Fungi produce septa to partition filamentous hyphae into discrete cells.