Septum (noun)

1. A dividing wall or membrane separating two cavities or masses of tissue in an organism.
2. A partition dividing a space or an organ into separate parts.

Origin:

Late latin, from latin, neuter of septus, past participle of separare 'to separate'.

Examples:

1. The nasal septum separates the right and left nasal cavities.
2. The heart has an interatrial septum and an interventricular septum.
3. The septum of the uterus divides it into two cavities.
4. In botany, the septum is the dividing wall in the ovary of a flower.
5. The brain is divided into two hemispheres by the longitudinal cerebral fissure, also called the interhemispheric sulcus or the cerebral septum.