# Dictionary Definition

perimeter

### Noun

1 the boundary line or the area immediately inside the boundary [syn: margin, border]
2 a line enclosing a plane areas
3 the size of something as given by the distance around it [syn: circumference]

# User Contributed Dictionary

## English

### Noun

1. The sum of the distance of all the lengths of the sides of an object.
2. The outer limits of an area. See Synonyms at circumference.
3. The length of such a boundary.
4. A fortified strip or boundary usually protecting a military position.

#### Translations

sum of the distance of all the lengths of the sides of an object
• Czech: obvod
• Dutch: omtrek, perimeter
• Finnish: kehä
• Spanish: perímetro
length of such a boundary
• Dutch: omtrek, perimeter
outer limits of an area
fortified strip or boundary usually protecting a military position

# Extensive Definition

The perimeter is the distance around a given two-dimensional object. The word perimeter is a Greek root meaning measure around, or literally "around measure".

## Practical uses

Calculations of perimeter and area have considerable practical applications. Perimeter is used in calculating the border of an object such as a yard or flowerbed when a fence or other border is being installed around the edges. Area is used when all the area inside of a perimeter is being covered with something, such as a yard being covered with sod or fertilizer.
In military usage, the term perimeter defines a geographic area of importance, such as a physical installation or defensive work, but can also refer to a theoretical construct such as an all-round defense formed by a small group of soldiers, the purpose of which is mutual protection of each other rather than defence of actual territory.

## Formulas

### Polygons

As a general rule, the perimeter of a polygon can always be calculated by adding all the length of the sides together. So, the formula for triangles is P=a+b+c, where a, b and c stand for each side of it. For quadrilaterals the equation is P=a+b+c+d. For equilateral polygons, P=na, where n is the number of sides and a is the measure of the side.

### Circles

For circles the equation is P = 2 \cdot \pi \cdot r
or P = d \cdot \pi
(The dot means multiply or times)

### In General

If r is considered to be the distance from the centre of a regular polygon to one of its vertices (or in the case of a circle, the radius), the following holds true:
P = \frac
• P stands for the perimeter,
• r stands for the radius
• A stands for the area