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One half ( : halves) is the
is also one of the few fractions to usually have a key of its own on
One half ( : halves) is the irreducible fraction
An irreducible fraction (or fraction in lowest terms, simplest form or reduced fraction) is a fraction in which the numerator and denominator are integers that have no other common divisors than 1 (and −1, when negative numbers are considered). ...
resulting from dividing one by two
2 (two) is a number, numeral and digit. It is the natural number following 1 and preceding 3. It is the smallest and only even prime number. Because it forms the basis of a duality, it has religious and spiritual significance in many cultur ...
or the fraction resulting from dividing any number by its double. Multiplication by one half is equivalent to division by two In mathematics, division by two or halving has also been called mediation or dimidiation. The treatment of this as a different operation from multiplication and division by other numbers goes back to the ancient Egyptians, whose multiplication alg ...
, or "halving"; conversely, division by one half is equivalent to multiplication by two, or "doubling". One half often appears in mathematical equations, recipes, measurements, etc. Half can also be said to be one part of something divided into two equal parts.
For instance, the area ''S'' of a triangle is computed.
:''S'' = × perpendicular height.
One half also figures in the formula for calculating figurate numbers
The term figurate number is used by different writers for members of different sets of numbers, generalizing from triangular numbers to different shapes (polygonal numbers) and different dimensions (polyhedral numbers). The term can mean
* polygo ...
, such as triangular number
A triangular number or triangle number counts objects arranged in an equilateral triangle. Triangular numbers are a type of figurate number, other examples being square numbers and cube numbers. The th triangular number is the number of dots i ...
s and pentagonal number
A pentagonal number is a figurate number that extends the concept of triangular and square numbers to the pentagon, but, unlike the first two, the patterns involved in the construction of pentagonal numbers are not rotationally symmetrical. The ...
s:
:
and in the formula for computing magic constants for magic square
In recreational mathematics, a square array of numbers, usually positive integers, is called a magic square if the sums of the numbers in each row, each column, and both main diagonals are the same. The 'order' of the magic square is the number ...
s
:
The Riemann hypothesis states that every nontrivial complex root of the Riemann zeta function
The Riemann zeta function or Euler–Riemann zeta function, denoted by the Greek letter (zeta), is a mathematical function of a complex variable defined as \zeta(s) = \sum_^\infty \frac = \frac + \frac + \frac + \cdots for \operatorname(s) > ...
has a real part equal to .
One half has two different decimal
The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral ...
expansions, the familiar 0.5 and the recurring
Recurring means occurring repeatedly and can refer to several different things:
Mathematics and finance
*Recurring expense, an ongoing (continual) expenditure
*Repeating decimal, or recurring decimal, a real number in the decimal numeral syste ...
0.49999999... It has a similar pair of expansions in any even base. It is common to believe these expressions represent distinct numbers: see the proof that 0.999... equals 1 for a detailed discussion of a related case. In odd bases, one half has no terminating representation, only a single representation with a repeating fractional component, such as 0.11111111... in ternary
Ternary (from Latin ''ternarius'') or trinary is an adjective meaning "composed of three items". It can refer to:
Mathematics and logic
* Ternary numeral system, a base-3 counting system
** Balanced ternary, a positional numeral system, useful ...
.
Particularities in writing and language
is also one of the few fractions to usually have a key of its own on typewriter
A typewriter is a mechanical or electromechanical machine for typing characters. Typically, a typewriter has an array of keys, and each one causes a different single character to be produced on paper by striking an inked ribbon selectivel ...
s (see fractions
A fraction (from la, fractus, "broken") represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight ...
). It also has its own code point
In character encoding terminology, a code point, codepoint or code position is a numerical value that maps to a specific character. Code points usually represent a single grapheme—usually a letter, digit, punctuation mark, or whitespace—but ...
in some early extensions of ASCII at 171 (ABhex). In Unicode
Unicode, formally The Unicode Standard,The formal version reference is is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, wh ...
, it has its own code unit at U+00BD (decimal 189) in the C1 Controls and Latin-1 Supplement
The Latin-1 Supplement (also called C1 Controls and Latin-1 Supplement) is the second Unicode block in the Unicode standard. It encodes the upper range of ISO 8859-1: 80 (U+0080) - FF (U+00FF). C1 Controls (0080–009F) are not graphic. Thi ...
block and a cross-reference in the Number Forms block, rendering as "½."
The HTML
The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaSc ...
entity is ½.
One half is also one of the few fractions which are commonly expressed in natural language
Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of met ...
s by suppletion rather than regular derivation: in English
English usually refers to:
* English language
* English people
English may also refer to:
Peoples, culture, and language
* ''English'', an adjective for something of, from, or related to England
** English national ide ...
, for example, compare ''"one half"'' against other regular formations like ''"one-sixth"''.
It is acceptable to write one half as a hyphenated word, "one-half" or non-hyphenated, "one half".
Code points
In the Unicode standard, the symbol ½ has the code point U+00BD ½ Vulgar Fraction One Half (HTML #0189· inherited from Latin-1)PC entry
* + (keeping Alt pressed until all 4 digits have been typed on the numeric keypad only)See also
*List of numbers
This is a list of notable numbers and articles about Notability, notable numbers. The list does not contain all numbers in existence as most of the Set (mathematics), number sets are infinite. Numbers may be included in the list based on their ...
*Division by two In mathematics, division by two or halving has also been called mediation or dimidiation. The treatment of this as a different operation from multiplication and division by other numbers goes back to the ancient Egyptians, whose multiplication alg ...
References
{{Fractions and ratiosHalf
One half ( : halves) is the irreducible fraction resulting from dividing one by two or the fraction resulting from dividing any number by its double. Multiplication by one half is equivalent to division by two, or "halving"; conversely, ...
Rational numbers