What is "cleavage"

Cleavage \Cleav"age\, n.

1. The act of cleaving or splitting.

2. (Crystallog.) The quality possessed by many crystallized substances of splitting readily in one or more definite directions, in which the cohesive attraction is a minimum, affording more or less smooth surfaces; the direction of the dividing plane; a fragment obtained by cleaving, as of a diamond. See Parting.

3. (Geol.) Division into lamin[ae], like slate, with the lamination not necessarily parallel to the plane of deposition; -- usually produced by pressure.

   Basal cleavage, cleavage parallel to the base of a crystal, or to the plane of the lateral axes.

   Cell cleavage (Biol.), multiplication of cells by fission. See Segmentation.

   Cubic cleavage, cleavage parallel to the faces of a cube.

   Diagonal cleavage, cleavage parallel to ta diagonal plane.

   Egg clavage. (Biol.) See Segmentation.

   Lateral cleavage, cleavage parallel to the lateral planes.

   Octahedral cleavage, Dodecahedral cleavage, or Rhombohedral cleavage, cleavage parallel to the faces of an octahedron, dodecahedron, or rhombohedron.

   Prismatic cleavage, cleavage parallel to a vertical prism.

1816, in geology, "action of splitting (rocks or gems) along natural fissures," from cleave (v.1) + -age. General meaning "action or state of cleaving or being cleft" is from 1867.\n

\nThe sense of "cleft between a woman's breasts in low-cut clothing" is first recorded 1946, defined in a "Time" magazine article [Aug. 5] as the "Johnston Office trade term for the shadowed depression dividing an actress' bosom into two distinct sections;" traditionally first used in this sense by U.S. publicist Joseph I. Breen (1888-1965), head of the Production Code Administration (replaced 1945 by Eric Johnston), enforcers of Hollywood self-censorship, in reference to Jane Russell's costumes and poses in "The Outlaw."

n. 1 The act of cleave or the state of being cleft. (from 19th c.) 2 (context mineralogy English) The tendency of a crystal to split along specific planes. (from 19th c.) 3 (context biology English) The repeated division of a cell into daughter cells after mitosis. (from 19th c.) 4 The hollow or separation between a woman's breasts, especially as revealed by a low neckline. (from 20th c.) 5 (context chemistry English) The splitting of a large molecule into smaller ones. 6 (context politics English) The division of voters into voting blocs.

1. n. the state of being split or cleft

2. the breaking of a chemical bond in a molecule resulting in smaller molecules

3. (embryology) the repeated division of a fertilised ovum [syn: segmentation]

4. the line formed by a groove between two parts (especially the separation between a woman's breasts)

5. the act of cleaving or splitting

Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the microscope and to the naked eye.

The preliminary assumption is that voters do not come in predefined groups of pros and cons for or against a certain subject. Ballot analysis assumes that voters opt for a certain party or decide for the solution or option that comes closest to their own position. Cleavage separates the voters into advocates and adversaries on a certain issue, or voting for a certain party. If you imagine parties on a horizontal line for a certain issue, cleavage is the vertical line that divides the parties into supporters and opponents of the issue.

Cleavage may refer to:

• Cleavage (breasts), partial exposure of the separation between a woman's breasts.
• Buttock cleavage, minor exposure of the buttocks and the gluteal cleft between them
• Toe cleavage, partial exposure of a woman's toes in shoes
• Cleavage (crystal), in mineralogy and materials science, is a process of splitting a single crystal.
• Cleavage (geology), Foliation perpendicular to stress as a result of ductile deformation. e.g. shales (shists)
• Cleavage (embryo), in embryology, is the division of cells in the early embryo.
• Cleavage (fiber), in optical fibers.
• Teeth cleavage or tooth cleavage, slang for Diastema (dentistry), the gap between a person's two front teeth.
• In cell biology, the Cleavage furrow is the indentation that begins the process of cleavage, by which animal cells undergo cytokinesis.
• Bond cleavage in chemistry and biochemistry
• Cleavage (politics) The divisions of society that cause people to vote differently
• Cleavage (molecular biology), cutting of the 3' signaling region from a newly synthesized pre-messenger RNA (pre-mRNA) molecule in the process of gene transcription.

Cleavage is the area between a woman's breasts lying over the sternum, and normally refers to what is visible with clothing that includes a low-cut neckline. In some cultures, display of cleavage is considered aesthetic or erotic, and may be associated with garments with low necklines that expose or highlight cleavage, such as ball gowns, evening gowns, lingerie, and swimwear. In these cultures, women have throughout history sought to enhance their physical attractiveness and femininity, within the context of changing fashions and cultural-specific norms of modesty of the time and place. The methods practised in appropriate contexts have included the accentuation and partial display of breasts, including cleavage. In some cultures any display of cleavage may be culturally taboo, illegal or otherwise socially disapproved.

In embryology, cleavage is the division of cells in the early embryo. The zygotes of many species undergo rapid cell cycles with no significant growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a compact mass called the morula. Cleavage ends with the formation of the blastula.

Depending mostly on the amount of yolk in the egg, the cleavage can be holoblastic (total or entire cleavage) or meroblastic (partial cleavage). The pole of the egg with the highest concentration of yolk is referred to as the vegetal pole while the opposite is referred to as the animal pole.

Cleavage differs from other forms of cell division in that it increases the number of cells without increasing the mass. This means that with each successive subdivision, the ratio of nuclear to cytoplasmic material increases.

Cleavage, in structural geology and petrology, describes a type of planar rock feature that develops as a result of deformation and metamorphism. The degree of deformation and metamorphism along with rock type determines the kind of cleavage feature that develops. Generally these structures are formed in fine grained rocks composed of minerals affected by pressure solution.

Cleavage is a type of rock foliation, a fabric element that describes the way planar features develop in a rock. Foliation is separated into two groups: primary and secondary. Primary deals with igneous and sedimentary rocks while secondary deals with rocks that undergo metamorphism as a result of deformation. Cleavage is a type of secondary foliation associated with fine grained rocks. For coarser grained rocks, schistosity is used to describe secondary foliation.

There is a variety of definitions for cleavage which may cause confusion and debate. The terminology used in this article is based largely on Passchier and Trouw (2005). They state that cleavage is a type of secondary foliation in fine grained rocks characterized by planar fabric elements that form in a preferred orientation. Some authors chose to use cleavage when describing any form of secondary foliation.