# Definition:Euclidean Space/Euclidean Topology/Real

## Definition

Let $\R^n$ be an $n$-dimensional real vector space.

Let $M = \struct {\R^n, d}$ be a real Euclidean $n$-space.

The topology $\tau_d$ induced by the Euclidean metric $d$ is called the **Euclidean topology**.

### Real Number Line

Let $\R$ denote the real number line.

Let $d: \R \times \R \to \R$ denote the Euclidean metric on $\R$.

Let $\tau_d$ denote the topology on $\R$ induced by $d$.

The topology $\tau_d$ induced by $d$ is called the **Euclidean topology**.

Hence $\struct {\R, \tau_d}$ is referred to as the **real number line with the Euclidean topology**.

### Real Number Plane

Let $\R^n$ be an $n$-dimensional real vector space.

Let $M = \struct {\R^2, d}$ be a real Euclidean space of $2$ dimensions.

The topology $\tau_d$ induced by the Euclidean metric $d$ is called the **Euclidean topology**.

The space $\struct {\R^2, \tau_d}$ is known as the **(real) Euclidean plane**.

## Also known as

The **Euclidean topology** is often called the **usual topology**.

## Also see

- Results about
**Euclidean spaces**can be found here.

## Source of Name

This entry was named for Euclid.

## Historical Note

Euclid himself did not in fact conceive of the Euclidean metric and its associated Euclidean space, Euclidean topology and Euclidean norm.

They bear that name because the geometric space which it gives rise to is **Euclidean** in the sense that it is consistent with Euclid's fifth postulate.

## Sources

- 1975: Bert Mendelson:
*Introduction to Topology*(3rd ed.) ... (previous) ... (next): Chapter $3$: Topological Spaces: $\S 2$: Topological Spaces: Example $2$

- 1978: Lynn Arthur Steen and J. Arthur Seebach, Jr.:
*Counterexamples in Topology*(2nd ed.) ... (previous) ... (next): Part $\text {II}$: Counterexamples: $28$. Euclidean Topology: $9$