I. ˈrējən noun
( -s )
Etymology: Middle English regioun, from Middle French region territory, region, from Latin region-, regio direction, territory, region, from regere to guide, rule + -ion-, -io -ion — more at right
1.
a. obsolete : realm , kingdom
b. : an administrative area, division, or district (as in Rome under Augustus or in Soviet Russia)
2.
a. : a major indefinite division of inanimate creation
in the dark regions of the night sky
the aquatic regions of the earth
b. : a sphere (as of activity or interest) subject to expressed or implied forces
the abstract region of higher mathematics
: field 2a
3. : a particular part of the world or universe (as natural waters, the sky, a particular galaxy): as
a. : a large tract of land : one of the large districts or quarters into which a space or surface is conceived of as divided ; broadly : an indefinite area of land (as a country, province, district, or tract)
there are few unknown regions left on earth
b. : a broad geographical area containing a population whose members possess sufficient historical, cultural, economic, and social homogeneity to distinguish them from others
the region of the Southwest in the U.S.
c.
(1) : a major area of the world that is to some degree isolated by climatic or physical barriers and that supports a characteristic fauna differing both qualitatively and quantitatively from that of other regions
faunal overlap of the Ethiopian and Oriental regions
(2) : an area often with distinct natural boundaries that is characterized by the prevalence of one or more vegetational climax types or by a mosaic of such types
the oak-chestnut region of the deciduous forest formation of eastern No. America
4.
a. : one of the major subdivisions into which the body or one of its parts may logically be divided
the nine regions of the abdomen
b. : an indefinite area surrounding a specified body part
a pain in the heart region
c. : space occupied by something : part in question, engaged, occupied, or under discussion
the region of highest concentration
5. : one of the portions or zones into which the atmosphere is divided according to height or the sea according to depth
the dark abyssal region of the sea
6. : a mathematical aggregate consisting of the totality of all values of an aggregate of continuous variables each varying over an interval
II. noun
: an open connected set together with none, some, or all of the points on its boundary