Noun

(en-noun)

The act, process or ability of concentrating; the process of becoming concentrated, or the state of being concentrated.

# The direction of attention to a specific object.

# The act, process or product of reducing the volume of a liquid, as by evaporation.

# The act or process of removing the dress of ore and of reducing the valuable part to smaller compass, as by currents of air or water.

A field or course of study on which one focuses, especially as a student in a college or university.

The proportion of a substance in a whole.

* {{quote-magazine, year=2013, month=July-August, author= Philip J. Bushnell, magazine=(American Scientist)

, title= Solvents, Ethanol, Car Crashes & Tolerance , passage=Surprisingly, this analysis revealed that acute exposure to solvent vapors at concentrations below those associated with long-term effects appears to increase the risk of a fatal automobile accident. Furthermore, this increase in risk is comparable to the risk of death from leukemia after long-term exposure to benzene, another solvent, which has the well-known property of causing this type of cancer.}}

# (chemistry) The amount of solute in a solution measured in suitable units (e.g., parts per million (ppm))

The matching game pelmanism.

Noun

(en noun)

A group or bunch of several discrete items that are close to each other.

a cluster of islands

* Spenser

Her deeds were like great clusters of ripe grapes, / Which load the bunches of the fruitful vine.

*{{quote-book, year=1907, author=

, chapter=7, title= The Dust of Conflict , passage=Then there was no more cover, for they straggled out, not in ranks but clusters , from among orange trees and tall, flowering shrubs

*{{quote-news, year=2011, date=December 29, author=Keith Jackson, work=Daily Record

, title= SPL: Celtic 1 Rangers 0 , passage=Charlie Mulgrew’s delicious deadball delivery was attacked by a cluster of green and white shirts at McGregor’s back post but Ledley got up higher and with more purpose than anyone else to thump a header home from five yards.}}

*{{quote-magazine, year=2013, month=May-June, author= William E. Conner

, title= An Acoustic Arms Race , volume=101, issue=3, page=206-7, magazine=(American Scientist) , passage=Earless ghost swift moths become “invisible” to echolocating bats by forming mating clusters close (less than half a meter) above vegetation and effectively blending into the clutter of echoes that the bat receives from the leaves and stems around them.}}

A number of individuals grouped together or collected in one place; a crowd; a mob.

* Milton

As bees / Pour forth their populous youth about the hive / In clusters .

* Shakespeare

We loved him; but, like beasts / And cowardly nobles, gave way unto your clusters , / Who did hoot him out o' the city.

(astronomy) A group of galaxies or stars that appear near each other.

(music) A secundal chord of three or more notes.

(phonetics) A group of consonants.

(computing) A group of computers that work together.

(computing) A logical data storage unit containing one or more physical sectors (see block).

(statistics) A significant subset within a population.

(military) Set of bombs or mines.

(army) A small metal design that indicates that a medal has been awarded to the same person before.

An ensemble of bound atoms or molecules, intermediate in size between a molecule and a bulk solid.