- published: 18 May 2016
- views: 55222
Geometry (Ancient Greek: γεωμετρία; geo- "earth", -metria "measurement") is a branch of mathematics concerned with questions of shape, size, relative position of figures, and the properties of space. A mathematician who works in the field of geometry is called a geometer. Geometry arose independently in a number of early cultures as a body of practical knowledge concerning lengths, areas, and volumes, with elements of a formal mathematical science emerging in the West as early as Thales (6th Century BC). By the 3rd century BC geometry was put into an axiomatic form by Euclid, whose treatment—Euclidean geometry—set a standard for many centuries to follow.Archimedes developed ingenious techniques for calculating areas and volumes, in many ways anticipating modern integral calculus. The field of astronomy, especially mapping the positions of the stars and planets on the celestial sphere and describing the relationship between movements of celestial bodies, served as an important source of geometric problems during the next one and a half millennia. Both geometry and astronomy were considered in the classical world to be part of the Quadrivium, a subset of the seven liberal arts considered essential for a free citizen to master.
A dash is one of several kinds of punctuation mark. Dashes are similar to hyphens, but differ from them primarily in length, and serve different functions. The most common versions of the dash are the en dash (–) and the em dash (—).
There are several forms of dash, of which the most common are:
Less common are the two-em dash (⸺) and three-em dash (⸻), both added to Unicode with version 6.1 as U+2E3A and U+2E3B. Windows character codes require that Num Lock be on.
The figure dash (‒) is so named because it is the same width as a digit, at least in fonts with digits of equal width. This is true of most fonts, not only monospaced fonts.
The figure dash is used when a dash must be used within numbers (e.g. phone number 555‒0199). It does not indicate a range, for which the en dash is used; nor does it function as the minus sign, which also uses a separate glyph.
The figure dash is often unavailable; in this case, one may use a hyphen-minus instead. In Unicode, the figure dash is U+2012 (decimal 8210). HTML authors must use the numeric forms ‒
or ‒
to type it unless the file is in Unicode; there is no equivalent character entity. In TeX, the standard fonts have no figure dash; however, the digits normally all have the same width as the en dash, so an en dash can be substituted when using standard TeX fonts.