# Enneagon vs. Nonagon — What's the Difference?

By Maham Liaqat & Urooj Arif — Updated on May 2, 2024
An enneagon is a nine-sided polygon, also known as a nonagon, with both terms used interchangeably in geometry.

## Key Differences

An enneagon is a geometric figure that features nine straight sides and nine angles, defining it as a non-regular or regular polygon depending on the equality of its sides and angles. Whereas, a nonagon refers to the same shape, highlighting its role in both everyday geometry and more complex mathematical contexts. Both terms are often used in mathematical education to introduce concepts of polygon classification and properties.
Enneagon, deriving from the Greek words for 'nine' ('ennea') and 'angle' ('gonia'), emphasizes the shape's Greek origins and classical geometrical studies. On the other hand, nonagon is derived from the Latin 'nonus' meaning 'nine' and the Greek 'gonia', showing a blend of linguistic roots. This illustrates the convergence of language and mathematics in terminology.
In terms of symmetry, a regular enneagon has nine lines of symmetry, assuming all sides and angles are equal, which is ideal for teaching symmetry and balance in geometry classes. Conversely, a nonagon can also be irregular, possessing no lines of symmetry, which is useful for discussions on asymmetry and varied geometric forms.
The use of the term enneagon might be more prevalent in academic and theoretical mathematics to emphasize traditional Greek geometrical terminology. Whereas nonagon is commonly used in contemporary mathematics education, reflecting a more straightforward linguistic approach that might be easier for students to remember and understand.
Both enneagon and nonagon are integral in discussing properties of polygons, especially in the context of Euclidean geometry where understanding the characteristics of various polygons forms the basis of more complex geometric study. Each term enriches the dialogue by providing different historical and linguistic perspectives, enhancing educational depth.

## Comparison Chart

### Origin of Name

Greek (ennea + gonia: nine angles)
Mixed Latin and Greek (nonus + gonia: nine angles)

### Symmetry

Regular enneagons have 9 lines of symmetry
Regular nonagons have 9 lines of symmetry, irregular have none

9 sides
9 sides

### Usage in Texts

More frequent in theoretical and classical studies
More common in modern educational contexts

### Linguistic Preference

Preferred in academic discussions emphasizing classical geometry
Preferred in practical teaching and easier linguistic assimilation

## Compare with Definitions

#### Enneagon

A polygon with nine angles and nine sides.
In our geometry class, we learned how to draw an enneagon.

#### Nonagon

Used in educational settings to teach polygon properties.
The lesson plan includes exercises on the properties of a nonagon.

#### Enneagon

A term used to describe a 9-gon in classical geometric studies.
The textbook on ancient geometries described an enneagon with perfect symmetry.

#### Nonagon

A nine-sided polygon, synonymous with enneagon.
For her art project, she created a large nonagon.

#### Enneagon

A figure often explored in advanced mathematics.
We studied the internal angles of an enneagon to understand polygonal angle sums.

#### Nonagon

A common figure in geometry, emphasizing simplicity and symmetry.
The nonagon is particularly interesting due to its nine lines of symmetry.

#### Enneagon

A shape that can be regular or irregular.
He designed a table in the shape of an irregular enneagon.

#### Nonagon

Can be either regular or irregular.
The park's layout was designed as a regular nonagon.

#### Enneagon

A nine-sided figure used in various mathematical contexts.
The enneagon can be regular or irregular, depending on its angles.

#### Nonagon

A basic shape studied in primary and secondary education.
Students learn to identify shapes like squares, triangles, and nonagons.

#### Enneagon

(geometry) A polygon with nine sides; a nonagon.

#### Nonagon

In geometry, a nonagon () or enneagon () is a nine-sided polygon or 9-gon. The name nonagon is a prefix hybrid formation, from Latin (nonus, "ninth" + gonon), used equivalently, attested already in the 16th century in French nonogone and in English from the 17th century.

#### Enneagon

A polygon or plane figure with nine sides and nine angles; a nonagon.

#### Nonagon

A polygon with nine sides and nine angles.

#### Nonagon

(geometry) A polygon with nine sides and nine angles; an enneagon.

#### Nonagon

A plane figure or polygon having nine sides and nine angles.

#### Nonagon

A nine-sided polygon

## Common Curiosities

#### Which term is more commonly used in mathematics?

'Nonagon' is more commonly used, especially in modern educational contexts, due to its simpler linguistic base.

#### What is a nonagon?

A nonagon is another term for a nine-sided polygon, identical to an enneagon.

#### Are enneagon and nonagon interchangeable terms?

Yes, enneagon and nonagon refer to the same geometric figure and are often used interchangeably.

#### Why are there two different names for a nine-sided polygon?

The two names arise from different linguistic roots; 'enneagon' from Greek and 'nonagon' from a combination of Latin and Greek.

#### What is an enneagon?

An enneagon is a nine-sided polygon, which can be regular or irregular depending on the equality of its sides and angles.

#### What are the properties of a regular enneagon/nonagon?

A regular enneagon or nonagon has nine equal sides and nine equal angles, each internal angle being 140 degrees.

#### What are some real-world applications of enneagons and nonagons?

Enneagons and nonagons may be used in architectural designs and tiling patterns that require nine-sided shapes.

#### How do the symmetries of regular and irregular enneagons/nonagons differ?

Regular enneagons/nonagons have nine lines of symmetry, whereas irregular versions have none.

#### Can an enneagon be constructed using a compass and straightedge?

No, a perfect regular enneagon cannot be constructed with just a compass and straightedge due to the constraints of classical geometric constructions.

#### How are enneagons and nonagons used in teaching geometry?

These shapes are used to teach students about polygon properties, symmetry, and angle calculations.

#### What types of symmetry does a regular nonagon exhibit?

A regular nonagon exhibits rotational symmetry of order 9 and 9 lines of mirror symmetry.

#### Why might someone choose to use the term enneagon over nonagon in certain contexts?

Someone might prefer "enneagon" in academic or historical discussions to align with the traditional Greek nomenclature used in classical geometry studies.

#### Is there a cultural significance to enneagons or nonagons?

While less culturally significant than other polygons like squares or hexagons, enneagons/nonagons can feature in artistic and religious symbolism in various cultures.

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