What is "cohesion"

Cohesion \Co*he"sion\, n. [Cf. F. coh['e]sion. See Cohere.]

1. The act or state of sticking together; close union.

2. (Physics) That from of attraction by which the particles of a body are united throughout the mass, whether like or unlike; -- distinguished from adhesion, which unites bodies by their adjacent surfaces.

   Solids and fluids differ in the degree of cohesion, which, being increased, turns a fluid into a solid.
   --Arbuthnot.

3. Logical agreement and dependence; as, the cohesion of ideas.
   --Locke.

1670s, from French cohésion, from Latin cohaesionem (nominative cohaesio) "a sticking together," noun of action from past participle stem of cohaerere "to stick together" (see cohere).

n. 1 State of cohering, or of working together. 2 (context physics chemistry English) Various intermolecular forces that hold solids and liquids together. 3 (context biology English) growing together of normally distinct parts of a plant. 4 (context computing English) degree to which different modules in a computing system are functionally dependent on others. 5 (context linguistics English) grammatical or lexical relationship between different parts of the same text.

1. n. the state of cohering or sticking together [syn: coherence, coherency, cohesiveness] [ant: incoherence]

2. (botany) the process in some plants of parts growing together that are usually separate (such as petals)

3. (physics) the intermolecular force that holds together the molecules in a solid or liquid

Cohesion is the fourth studio album by Australian rock band Gyroscope, released through Island Records on 9 April 2010. It peaked at No. 3 on the ARIA Albums Chart.

The album's first single "Some of the Places I Know" was released on 1 February 2010, and the second single "Baby, I'm Gettin' Better" was released on 17 May. The third single, What Do I Know About Pain? was released on 1 October 2010. All three songs have had music videos provided for them. The first two singles have peaked within the top 40 of the ARIA Singles Charts.

In computer programming, cohesion refers to the degree to which the elements of a module belong together. Thus, cohesion measures the strength of relationship between pieces of functionality within a given module. For example, in highly cohesive systems functionality is strongly related.

Cohesion is an ordinal type of measurement and is usually described as “high cohesion” or “low cohesion”. Modules with high cohesion tend to be preferable, because high cohesion is associated with several desirable traits of software including robustness, reliability, reusability, and understandability. In contrast, low cohesion is associated with undesirable traits such as being difficult to maintain, test, reuse, or even understand.

Cohesion is often contrasted with coupling, a different concept. High cohesion often correlates with loose coupling, and vice versa. The software metrics of coupling and cohesion were invented by Larry Constantine in the late 1960s as part of Structured Design, based on characteristics of “good” programming practices that reduced maintenance and modification costs. Structured Design, cohesion and coupling were published in the article and the book ; the latter two subsequently became standard terms in software engineering.

In object-oriented programming, if the methods that serve a class tend to be similar in many aspects, then the class is said to have high cohesion. In a highly cohesive system, code readability and reusability is increased, while complexity is kept manageable.

Cohesion is increased if:

• The functionalities embedded in a class, accessed through its methods, have much in common.
• Methods carry out a small number of related activities, by avoiding coarsely grained or unrelated sets of data.

Advantages of high cohesion (or “strong cohesion”) are:

• Reduced module complexity (they are simpler, having fewer operations).
• Increased system maintainability, because logical changes in the domain affect fewer modules, and because changes in one module require fewer changes in other modules.
• Increased module reusability, because application developers will find the component they need more easily among the cohesive set of operations provided by the module.

While in principle a module can have perfect cohesion by only consisting of a single, atomic element – having a single function, for example – in practice complex tasks are not expressible by a single, simple element. Thus a single-element module has an element that either is too complicated, in order to accomplish task, or is too narrow, and thus tightly coupled to other modules. Thus cohesion is balanced with both unit complexity and coupling.

Cohesion (from Latin cohaerere "stick or stay together") or cohesive attraction or cohesive force is the action or property of like molecules sticking together, being mutually attractive. It is an intrinsic property of a substance that is caused by the shape and structure of its molecules, which makes the distribution of orbiting electrons irregular when molecules get close to one another, creating electrical attraction that can maintain a microscopic structure such as a water drop. In other words, cohesion allows for surface tension, creating a "solid-like" state upon which light (in weight) or low-density materials can be placed.

Water, for example, is strongly cohesive as each molecule may make four hydrogen bonds to other water molecules in a tetrahedral configuration. This results in a relatively strong Coulomb force between molecules. In simple terms, the polarity (state of which a molecule is oppositely charged on its poles) of water molecules allows them to be attracted towards each other. The polarity is due to the electronegativity of the atom of oxygen ; oxygen is more electronegative than the atoms of hydrogen, so the electrons they share through the covalent bonds are more often close to oxygen rather than hydrogen: these are called polar covalent bonds, covalent bonds between atoms that thus become oppositely charged. In the case of a water molecule, the hydrogen atoms carry positive charges while the oxygen atom has a negative charge. This charge polarization within the molecule allows it to align with adjacent molecules through strong intermolecular hydrogen bonding, rendering the bulk liquid cohesive. Van der Waals gases such as methane, however, have weak cohesion due only to Van der Waals forces that operate by induced polarity in non-polar molecules.

Cohesion, along with adhesion (attraction between unlike molecules), helps explain phenomena such as meniscus, surface tension and capillary action.

Mercury in a glass flask is a good example of the effects of the ratio between cohesive and adhesive forces. Because of its high cohesion and low adhesion to the glass, mercury does not spread out to cover the top of the flask, and if enough is placed in the flask to cover the bottom, it exhibits a strongly convex meniscus, whereas the meniscus of water is concave. Mercury will not wet the glass, unlike water and many other liquids, and if the glass is tipped, it will 'roll' around inside.

Cohesion may refer to:

• Cohesion (chemistry), the intermolecular attraction between like-molecules
• Cohesion (computer science), a measure of how well the lines of source code within a module work together
• Cohesion (geology), the part of shear strength that is independent of the normal effective stress in mass movements
• Cohesion (linguistics), the linguistic elements that make a discourse semantically coherent
• Cohesion (band), a musical group from Surrey, England
• Cohesion (album), the fourth studio album by Australian band Gyroscope
• Cohesion (social policy), the bonds or "glue" between members of a community or society and life

Cohesion are a four-piece indie rock band from Manchester. The group are:

• Andrew O'Hara - vocals, guitar.
• Kevin McPhillips - lead guitar.
• Simon Harrison - bass.
• Geoff Burroughs - drums, percussion.

The band were formed by O'Hara and McPhillips in 2003. Burroughs joined the duo in 2004, with Harrison completing the line-up in 2005. After a sustained period of playing gigs at local venues, the group have released two EPs independently, Cohesion EP and Shadows In The Shade EP (named after a lyric in the song 'Can't Ignore') to critical acclaim in the local press and internet music sites.

The band consider their influences to be bands such as The La's, Coldplay, The Flaming Lips, David Bowie, The Beach Boys, Culture Club, Wham!, and the Butthole Surfers. amongst others. Reviews of the band have noted the band's distinct 'West Coast' sound.

Cohesion are currently residing in Levenshulme, Manchester.

Cohesion is the grammatical and lexical linking within a text or sentence that holds a text together and gives it meaning. It is related to the broader concept of coherence.

There are two main types of cohesion: grammatical cohesion which is based on structural content, and lexical cohesion which is based on lexical content and background knowledge. A cohesive text is created in many different ways. In Cohesion in English, M.A.K. Halliday and Ruqaiya Hasan identify five general categories of cohesive devices that create coherence in texts: reference, ellipsis, substitution, lexical cohesion and conjunction.

Cohesion is the component of shear strength of a rock or soil that is independent of interparticle friction.

In soils, true cohesion is caused by following:

1. Electrostatic forces in stiff overconsolidated clays (which may be lost through weathering)
2. Cementing by Fe O, Ca CO, Na Cl, etc.

There can also be apparent cohesion. This is caused by:

1. Negative capillary pressure (which is lost upon wetting)
2. Pore pressure response during undrained loading (which is lost through time)
3. Root cohesion (which may be lost through logging or fire of the contributing plants, or through solution)