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Related to perivascular space: Lacunar Infarct


a. the region beyond the earth's atmosphere containing the other planets of the solar system, stars, galaxies, etc.; universe
b. (as modifier): a space probe
a. the region beyond the earth's atmosphere occurring between the celestial bodies of the universe. The density is normally negligible although cosmic rays, meteorites, gas clouds, etc., can occur. It can be divided into cislunar space (between the earth and moon), interplanetary space, interstellar space, and intergalactic space
b. (as modifier): a space station
3. Music any of the gaps between the lines that make up the staff
4. Maths a collection of unspecified points having properties that obey a specified set of axioms


The near-vacuum existing beyond the atmospheres of all bodies in the Universe. The extent of space, i.e. whether it is finite or infinite, is as yet unresolved. See intergalactic medium; interplanetary medium; interstellar medium.


The unlimited continuous three-dimensional expanse in which all material objects exist; all the area in and around a structure, or volume between specified boundaries, and the interval between two objects.



in mathematics, a logically conceivable form or structure that is used as a setting in which other forms and various constructions are realized. For example, in elementary geometry the plane or space is the setting in which various figures are constructed. In most spaces, we introduce relations whose formal properties are similar to those of ordinary spatial relations, such as distance between points or congruence of figures. Consequently, such spaces may be said to represent logically conceivable spacelike forms.

Historically, the first mathematical space was three-dimensional Euclidean space, which is an approximate abstract image of physical space; it has remained a very important space in mathematics. The general concept of space took shape in mathematics as a result of the gradual, increasingly broad generalization and modification of the concepts of the geometry of Euclidean space. The first spaces differing from three-dimensional Euclidean space were introduced in the first half of the 19th century. These spaces were Lobachevskian space and n-dimensional Euclidean space. The general concept of mathematical space was advanced in 1854 by B. Riemann. The process of generalizing, refining and concretely defining the concept followed various directions; for example, such concepts as vector space, Hilbert space, Riemannian space, function space, and topological space were developed.

In contemporary mathematics a space is defined as a set of objects, which are called the points of the space. These objects may be. for example, geometric figures, functions, or the states of a physical system. When we consider a set of objects as a space, we deal not with the individual properties of the objects but with only those properties of the set that are determined by relations that we wish to take into account or that we introduce by definition. These relations between points and various configurations, or sets of points, determine the geometry of the space. When the geometry is constructed axiomatically, the basic properties of these relations are expressed in the corresponding axioms.

Three examples of spaces are metric spaces, spaces of events, and phase spaces. In a metric space, the distance between points is defined. Thus, the functions f(x) continuous on an interval [a, b] form a metric space—whose points are the functions f (x)— when the distance between f1(x) and f2(x) is defined as the maximum of the absolute value of the difference between the two functions:

r = max ǀf1(x) –f2(x

The concept of space of events plays an important role in the geometric interpretation of the theory of relativity. Every event is characterized by its position—the coordinates x, y, and z— and the time t of its occurrence. The set of all possible events is thus a four-dimensional space, in which an event or point is defined by the four coordinates x, y, z, and t.

Phase spaces are studied in theoretical physics and mechanics. The phase space of a physical system is the set of all the possible states of the system. The states are the points of the space.

The spaces in these examples are of significance in the actual universe since the set of possible states of a physical system or the set of events with space and time coordinates has real existence. Consequently, we are dealing with forms of reality that, although not spatial in the ordinary sense, are spacelike in structure. The question of which mathematical space reflects most accurately the general properties of physical space is answered experimentally. Thus, it has been established that in describing physical space Euclidean geometry is not always sufficiently accurate, and Riemannian geometry is used in the present-day theory of physical space (seeRELATIVITY, THEORY OF). The concept of space in mathematics is also discussed in the articles GEOMETRY, MATHEMATICS, and MULTIDIMENSIONAL SPACE.



Specifically, the part of the universe lying outside the limits of the earth's atmosphere.
More generally, the volume in which all celestial bodies, including the earth, move.
The open-circuit condition or the signal causing the open-circuit condition in telegraphic communication; the closed-circuit condition is called the mark.
In context, usually a set with a topology on it or some other type of structure.


The space character, ASCII 32.

See octal forty.


(1) In digital electronics, a 0 bit. Contrast with mark.

(2) The trendy word that started in the 1990s for area or field of endeavor. For example, the phrase "we are involved in the videoconferencing space" refers simply to the videoconferencing industry. To many, this sounds more chic than using a word such as "field," "arena" or "industry."
References in periodicals archive ?
15) In this African grey parrot, AQP4 was overexpressed in the whole brain, especially in the striatum, cerebral cortex, hippocampus, cerebellum, and perivascular spaces.
They are T2 and FLAIR hyperintense and usually isointense to cerebrospinal fluid signal intensity because of distention of the small vessel perivascular spaces (7-9).
Leptomeningeal enhancement as well as enhancement extending into the perivascular spaces may also be seen (Figures 6C, D, E, and F).
Amebic trophozoites were present in high numbers, often located in perivascular spaces (Figure 1B), and cysts were conspicuously absent, a characteristic feature of PAM.
3) Infiltration occurs along white matter tracts and perivascular spaces, leading to distant spread despite minimal underlying architectural distortion.
The fibroblasts cannot be essential, because in the liver amyloid is found in the perivascular spaces between portal capillaries and liver cells, in which fibroblasts are absent.
CNS vascular lesions, characterized by perivascular hemorrhage and edema, mononuclear cell infiltration of perivascular spaces, perivascular fibrin deposits and necrosis of small vessels were seen in dogs treated with simvastatin at a dose of 360 mg/kg/day, a dose that produced plasma drug levels that were about 50 times higher than the mean drug levels in humans taking 40 mg/day.
Perivascular spaces, occasional rosettes, and scattered aggregates of small mature lymphocytes were also seen.

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