# Definition:Left-Total Relation

Jump to navigation
Jump to search

## Definition

Let $S$ and $T$ be sets.

Let $\RR \subseteq S \times T$ be a relation in $S$ to $T$.

Then $\RR$ is **left-total** if and only if:

- $\forall s \in S: \exists t \in T: \tuple {s, t} \in \RR$

That is, if and only if every element of $S$ relates to some element of $T$.

## Also known as

A **left-total relation** $\RR \subseteq S \times T$ is also sometimes referred to as:

- A
**total relation**, but this can be confused with a connected relation - A
**relation on $S$**, but this can be confused with an endorelation - A
**multiple-valued function**or**multifunction**, but the latter is usually reserved for complex functions

The term **left-total relation** is usually preferred.

## Multifunction

In the field of complex analysis, a **left-total relation** is usually referred to as a **multifunction**.

## Also see

- Definition:Serial Relation: a relation $\RR: S \to S$ which is
**left-total**

## Sources

- 1968: A.N. Kolmogorov and S.V. Fomin:
*Introductory Real Analysis*... (previous) ... (next): $\S 1.4$: Decomposition of a set into classes. Equivalence relations - 1972: Murray R. Spiegel and R.W. Boxer:
*Theory and Problems of Statistics*(SI ed.) ... (previous) ... (next): Chapter $1$: Functions