Number
A number (Wiktionary -- Number (http://wiktionary.org/wiki/Number)) is an abstract entity used to describe quantity. There are different types of numbers: the relationships between natural numbers, integers, rational numbers, irrational numbers and real numbers can be represented by a Venn diagram (in which the set of real numbers is viewed as a rectangle; with irrational numbers forming one part of the rectangle and rational numbers forming the other; and with integers being represented by a circle within the set of rational numbers, and natural numbers represented by a circle within the set of integers).Numbers should be distinguished from numerals which are symbols used to represent numbers. The notation of numbers as series of digits is discussed in numeral systems. People like to assign numbers to objects. There are various numbering schemes for doing so. The arithmetical operations of numbers, such as addition and multiplication, are generalized in the branch of mathematics called abstract algebra; one obtains the groups, rings and fields.
The most familiar numbers are the natural numbers (0, 1, 2, ...) used for counting[?] and denoted by N. If negative numbers are included, one obtains the integers Z. Ratios of integers are called rational numbers or fractions; the set of all rational numbers is denoted by Q. If all infinite and non-repeating decimal expansions are included, one obtains the real numbers R, which are in turn extended to the complex numbers C in order to be able to solve all algebraic equations. The above symbols are generally written in blackboard bold.
Extensions
Newer developments are the hyperreal numbers and the surreal numbers which extend the real numbers by adding infinitesimal and infinitely large numbers. While (most) real numbers have infinitely long expansions to the right of the decimal point, one can also try to allow for infinitely long expansions to the left, leading to the p-adic numbers. For measuring the size of infinite sets, the natural numbers have been generalized to the ordinal numbers and to the cardinal numbers.
Particular Numbers
See: List of numbers, even and odd numbers, mathematical constant, negative and non-negative numbers, small numbers, large numbersWhy linger here?
Lest I should look on it and call it dear.
For if I love thee thou wilt sooner die;
Midnight will fall from the revengeful sky.html">sky
Call not my name.html">name, nor heed if thine I crave,
And bathe thee in the all-effacing wave.
But upward still thy perilous footsteps fare
Dilating on a tide of crystal air
Out of mid-heaven and makes my soul its glass?
Thy tarrying smile? Oh, veil thy lips and pass.
Nay . . . pause and let me name thee! For I see,
Strange hour.html">hour that wilt not loose thy hold on me,
From hand.html">hand to hand they toss the flying fire,
About the wheeling music of the Lyre.
Dread hour that lead'st the immemorial round,
The thronging splendours that the day held bound,
Forth from itself, and flings its ray ahead,
To where our lives are but the ages' tread,
And let this year be, not the last of youth,
If more remote from hope, yet nearer truth,
ALL SOULS
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A THIN moon faints in the sky o'erhead,
Walk we not, Sweet, by garden ways,
But forth of the gate and down the road,
For it's turn of the year and All Souls' night.html">night,
Fear not that sound like wind in the trees:
Fear not the shudder that seems to pass:
Fear not the drip of the bough as you stoop:
For the year's on the turn and it's All Souls' night,
And where should a man bring his sweet to woo
Where lie the dead lips that thirst to kiss,
Where the maid and her lover, from sere to.
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