General terms:
* Separation: This is a neutral term that implies a physical or conceptual division.
* Division: Similar to separation, but often emphasizes a more distinct split.
* Discrimination: This focuses on unfair treatment based on group affiliation.
* Exclusion: This highlights the act of keeping someone or something out.
* Isolation: This refers to the state of being separated and alone.
Specific to race/ethnicity:
* Apartheid: A specific system of racial segregation and discrimination, particularly used in South Africa.
* Jim Crow: Refers to the laws and customs of racial segregation in the American South.
* Segregation: While the word itself is a noun, it's also the most direct and widely understood term for the practice.
Other contexts:
* Stratification: This emphasizes a hierarchical division within a society.
* Categorization: This highlights the process of grouping based on specific characteristics.
* Partition: This refers to the act of dividing a space or group into separate parts.
The best noun to use will depend on the specific situation and the nuance you want to convey.