 pace

a historic unit of distance between two successive falls of person's same
foot, equals two steps. The Romans counted 1000 paces in a mile with each
pace being a little over 58 inches (or about 148 centimeters).
The pace is usually defined to be exactly 5 feet (or 152.4 centimeters); this
unit is also called the great pace or geometrical pace.
However, "pace" is often used as an alternate name for the step in
military use.
 pack

a commercial unit specifying the number of items per package.
 packen

a traditional Russian unit of weight equal to 1200 funte, 30 pudi, 1083 pounds,
or 491.4 kilograms.
 page

a unit of information or data in computer science, usually equal to 256 bytes.
a single byte can store the address of a location within a page.
 pair

a unit of quantity equal to 2. The word is from the Latin paria ,
meaning "equals." Originally a pair was simply a group of similar
objects. Now it refers to a group of two.
 palm

Historic unit of distance, there are two versions of palms: Shorter palm equals
to the width of a person's palm. It equals 4 digits or 1/6 cubit,
about 3 inches or 7.5 centimeters. Longer palm equals to
the length of a person's hand, from the wrist to the end of the middle finger.
In the English system this unit is equal to 9 inches (22.86 centimeters) and is
usually called a span. In Roman times, the longer unit was
known as the palmus major and the shorter one as the palmus
minor. In the nineteenth century, the 3inch version
was more common in Britain, and the 9inch version was more common in the
U.S.
palm sometimes used in Dutch for the decimeter (10
centimeters, or about 3.937 inches).
 palmo

a traditional unit of distance in Spain and Portugal. It is about 20.9
centimeters in Spain and a little more than that in Spanish Latin America.This
unit was based on the width of a person's outstretched hand, from the tip
of the thumb to the tip of the little finger, a definition identical to that of
the English span.
 parasang

a historic unit of distance. The unit originated in Persia but was used
throughout the ancient Middle East and Mediterranean. It was equal to roughly
3.54.0 miles or about 6 kilometers. In Arabic the unit is called the farasang.
 Paris point

a unit of length equal to 2/3 centimeter (0.59 inch) used to measure shoe size
in European countries.
 pascal (Pa)

the SI unit of pressure. The pascal is the standard pressure unit in the MKS
metric system, equal to "one newton per square meter" or one "kilogram per
meter per second per second." Air pressure is also measured in hectopascals
(hPa), with 1 hPa = 1 millibar. The unit is named for Blaise Pascal
(16231662), French philosopher and mathematician, who was the first person to
use a barometer to measure differences in altitude.
 pé

the traditional Portuguese foot, equal to 12 polegadas or about 33.324
centimeters or 13.12 inches.
 pearl grain

a unit of mass equal to 1/4 carat or 50 milligrams; see grain.
 peck

a traditional unit of volume, formerly used for both liquids and solids, mostly
for dry commodities such as grains, berries, and fruits. A peck is 2 gallons, 8
quarts, or 1/4 bushel. In the U. S., a peck holds 537.605 cubic inches or
approximately 8.8098 liters. In the British imperial system, a peck is a little
larger, holding 554.84 cubic inches or approximately 9.0923 liters. The word
"peck", comes from the name of a similar old French unit.
 pencil hardness

a traditional measure of the hardness of the "leads" in pencils. The
hardness scale, from softer to harder. In the U.S., many manufacturers use a
numerical scale in which the grades B, HB, F, H, 2H correspond approximately to
numbers 1, 2, 21/2, 3, and 4, respectively. This hardness scale is analogous
to the wellknown Mohs hardness scale used in geology to
measure the hardness of minerals.
 pennyweight (dwt or pwt)

a unit of weight in the traditional troy system, equal to 24 grains or 1/20
troy ounce. One pennyweight is about 1.5552 gram. The d in the traditional
symbol dwt is from the Latin word denarius for the small coin which
was the Roman equivalent of a penny.
 pentad

a unit of quantity equal to 5.
 per annum (PA)

a traditional unit of frequency equal to once a year.
 percent(%)

a unit of proportion, equal to 0.01. The word is Latin, meaning "by the
hundred." The symbol % can be placed after any number; mathematically,
its effect is an immediate division by 100.
 percentile

a unit used in statistics to describe a portion of the individuals or events
being studied. Suppose the data are arranged by numerical scores, from highest
to lowest. A score belongs to the 78th percentile, for example, if it is
greater than 78% of the scores but it is not greater than 79% of the scores.
This procedure divides the scores into 100 percentiles, numbered 0th through
99th.
 perch

an alternate name for the rod (16.5 feet or 5.0292 meters). The word perch
comes from the Latin pertica (pole).

The Romans also had a distance unit called the pertica, but it was
shorter: 10 Roman feet (9.71 English feet or 2.96 meters).

French "perche" equals 18 pieds or 3 toises. By legal definition in
Canada it equals 19.1835 English feet or 5.847 13 meters.

Ireland standardized perch at 21 English feet (6.4008 meters) or 14/11
English perch or rod

perch is also a unit of area equal to one square perch (length). A perch of
area covers exactly 272.25 square feet or about 25.292 85 square meters. There
are 40 perches in a rood and 160 perches in an acre.
 peta

a metric prefix denoting 10^{15} (one U.S. quadrillion). The prefix was
chosen to suggest the Greek penta
 pfund

a traditional German weight unit corresponding to the English pound . The pfund
is equal to 16 unze or 32 lot. The various German states adopted
different standards, ranging from the English pound (454 grams) to the
Viennese pfund at about 1.2 pounds (560 grams). In the late nineteenth century,
the pfund was redefined as a metric unit equal to exactly 500 grams (about
1.102 31 pound).
 pico

a metric prefix denoting 10^{12} (trillionth). It is coined from the
Italian piccolo, small.
 picul

a unit of weight widely used in East Asia during the colonial period. The picul
is equal to 100 catties, about 133.3 pounds or 60.5 kilograms. A metric
unit equal to 60 kilograms (132.28 pounds) in Thailand.
 pie

the traditional foot of Spain, equals 1/3 vara or 12 pulgadas, about 27.86
centimeters or 10.97 inches; the pie is generally longer in the Latin America .
The Argentine pie is 28.89 centimeters or 11.37 inches.
 piece

a unit of quantity, equal to 1, represents an exact count of items.
 pied

the traditional French foot, called the Paris foot in English. It equals
about 32.48 centimeters or 12.79 inches; the official Canadian definition is
12.789 inches (32.484 06 centimeters), In French Canada, pied is
generally used to refer to the English foot.
 piede

the traditional Italian foot, one common length was about 29.8 centimeters.
 pik or pic

a traditional unit of distance in the Eastern Mediterranean and Near East. A
typical value is about 28 inches (71 centimeters). This is an "arm" unit, like
the Italian braccio and the Russian arshin.
 pin

a traditional British unit of volume for beer. It is equal to 1/8 barrel or 4.5
imperial gallons (20.457 liters).
 ping

a traditional unit of area in Taiwan(China), equal to about 3.305 square meters
(3.953 square yards). The same unit in Korea as the pyong.
 pint

a traditional unit of volume equal to 1/2 quart. There are three different
pints: the U. S. liquid pint, equal to exactly 28.875 cubic inches, 16 fluid
ounces, or approximately 473.176 milliliters; the U. S. dry pint, equal
to 33.600 cubic inches or approximately 550.611 milliliters; the British
Imperial pint, equal to 20 British fluid ounces, 34.678 cubic inches or
approximately 568.261 milliliters.
 pipa

a traditional Portuguese unit of liquid volume, similar in size to the English pipe
The pipa equals to 500 liters, which is 0.5 cubic meter, 132.085 U.S.
gallons, or 109.996 British imperial gallons.
 pipe

a traditional unit of liquid volume. a pipe equals 126 U.S.gallons, about
16.844 cubic feet or 476.96 liters In the U.S..
 pitch

a unit used in printing, means "characters per inch" .
 pixel

a picture element. Pixels are often used to measure the resolution (or
sharpness) of images.
 point

a unit of proportion, equal to 0.01 or 1%, often called a percentage point.
a unit of quantity equal to 1. This unit is used to express changes in an
arbitrary score or index.
 pond

the Dutch pound, historically about 494 grams (1.089 English pounds).
 pouce

the French "inch" unit, equal to 1/12 pied.
 pound

a traditional unit of mass or weight. The unit now in general use in the United
States is the avoirdupois pound, is divided into 16
ounces. By international agreement, one avoirdupois pound is equal to exactly
453.592 37 grams; this is exactly 175/144 = 1.215 28 troy pounds.

The troy pound, named for the French market town of Troyes, was the unit used
in England by apothecaries and jewelers, is divided into 12 ounces like the
Roman pound. One troy pound is 373.242 grams, or 0.822 858
avoirdupois pounds (13.165 avoirdupois ounces). The troy
and avoirdupois pounds are connected by the grain:
5760 grains in a troy pound and 7000 grains in an avoirdupois pound.
 pous

the ancient Greek foot, a unit of distance equal to about 30.7 centimeters, a
little longer than the modern English foot. The plural is podes
 pulgada

the Spanish inch, equal to 1/12 pie. It varies from about 23.2 to 24.1
millimeters (0.913 to 0.949 inch).
 pyong

a Korean unit of area equal to about 3.306 square meters or 3.954 square yards.
The pyong is widely used in Korea to measure areas both inside and outside
buildings.
