Definition:Quotient Set
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Definition
Let $\RR$ be an equivalence relation on a set $S$.
For any $x \in S$, let $\eqclass x \RR$ be the $\RR$-equivalence class of $x$.
The quotient set of $S$ induced by $\RR$ is the set $S / \RR$ of $\RR$-classes of $\RR$:
- $S / \RR := \set {\eqclass x \RR: x \in S}$
Also known as
The quotient set of $S$ induced by $\RR$ can also be referred to as:
- the quotient of $S$ determined by $\RR$
- the quotient of $S$ by $\RR$
- the quotient of $S$ modulo $\RR$
The notation $\overline S$ can occasionally be seen for $S / \RR$.
If $\PP = S / \RR$ is the partition formed by $\RR$, the quotient set can be denoted $S / \PP$.
Also see
- Results about quotient sets can be found here.
Linguistic Note
The word quotient derives from the Latin word meaning how often.
Sources
- 1951: Nathan Jacobson: Lectures in Abstract Algebra: Volume $\text { I }$: Basic Concepts ... (previous) ... (next): Introduction $\S 3$: Equivalence relations
- 1960: Paul R. Halmos: Naive Set Theory ... (previous) ... (next): $\S 7$: Relations
- 1965: Seth Warner: Modern Algebra ... (previous) ... (next): Chapter $\text {II}$: New Structures from Old: $\S 10$: Equivalence Relations
- 1967: George McCarty: Topology: An Introduction with Application to Topological Groups ... (previous) ... (next): Chapter $\text{I}$: Sets and Functions: Quotient Functions
- 1971: Allan Clark: Elements of Abstract Algebra ... (previous) ... (next): Chapter $1$: Equivalence Relations: $\S 17$
- 1972: A.G. Howson: A Handbook of Terms used in Algebra and Analysis ... (previous) ... (next): $\S 3$: Equivalence relations and quotient sets: Quotient sets
- 1975: T.S. Blyth: Set Theory and Abstract Algebra ... (previous) ... (next): $\S 6$. Indexed families; partitions; equivalence relations
- 1975: Bert Mendelson: Introduction to Topology (3rd ed.) ... (previous) ... (next): Chapter $1$: Theory of Sets: $\S 7$: Relations
- 1982: P.M. Cohn: Algebra Volume 1 (2nd ed.) ... (previous) ... (next): Chapter $1$: Sets and mappings: $\S 1.4$: Equivalence relations
- 1996: Winfried Just and Martin Weese: Discovering Modern Set Theory. I: The Basics ... (previous) ... (next): Part $1$: Not Entirely Naive Set Theory: Chapter $1$: Pairs, Relations, and Functions
- 2002: Thomas Jech: Set Theory (3rd ed.) ... (previous) ... (next): Chapter $1$: Power Set
- 2010: Steve Awodey: Category Theory (2nd ed.) ... (previous) ... (next): $\S 3.4$