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1. The degree of firmness of a solid, as determined by its resistance to deformation, scratching, or abrasion.
See also: hardness scale, number.
2. The relative penetrating power of a beam of x-rays, used both within the diagnostic range of energy and in radiation therapy; expressed in terms of half-value layer.


Etymology: AS, heard, hard
1 a quality of water produced by soluble salts of calcium and magnesium or other substances that form a precipitate with soap and thus interfere with its cleansing power.
2 the quality of firmness produced by cohesion of the particles composing a substance, as evidenced by its inflexibility or resistance to indentation, distortion, or scratching.


1. The degree of firmness of a solid, as determined by its resistance to deformation, scratching, or abrasion.
2. The relative penetrating power of a beam of x-rays.

hardness (of a substance),

n the ability of a material to resist an indenting type of load.
hardness (of radiographs),
n a term used to indicate in a general way the quality of x-radiation, with hardness being a function of the wavelength; the shorter the wavelength, the harder the x-radiation.
hardness, Mohs,
n a relative scratch resistance of minerals based on an arbitrary scale: 10, diamond; 9, corundum; 8, topaz; 7, quartz; 6, orthoclase; 5, apatite; 4, fluorite; 3, calcite; 2, gypsum; and 1, talc.
hardness tests,
See tests, hardness.

Patient discussion about hardness

Q. Why is it so hard???? Why is it so hard to quit drinking ? i try and i try and it seems like i can't find the strength to stop completely .. every time i am almost there .. but than i just snap!

A. HI....find out about alcoholics anonymous in your town,call their 800#...go to(INTHEROOMS.com)find HELP.......mrfoot56

Q. i cant stop getting a hard on erection stiffy embarrassing crease in trousers

A. Have you heard of priapism,a condition in which the penis is continually erect; usually painful and seldom with sexual arousal. If you suffer from this you should go see a doctor about it.

Q. anyone knows how to stop hard skin on the feet from becoming cracked??? during summer my feet got lots of hard skin and in the heel area the skin actually got cracked kinda deep. it hurts now and the cracks are starting to get infected I guess... do u guys know how to solve this?? I know there are some creams for that but I thought maybe now it's too late for that and I need something stronger?

A. There are good creams for moisterizing the skin of your feet on a daily basis, however now that you feel they might be infected you should see a dermatologist for some better treatment.

More discussions about hardness
References in periodicals archive ?
Variability: Metal castings are not homogenous, and hardness variations will occur throughout the typical casting, though the variation between locations should not be dramatic.
So, the hardness of water may be one of the characteristics of processing water that should be monitored by poultry processors.
Moreover, as the load force weakens and enters the area of micro-hardness, the Vickers hardness is no more depending on the power of applied load (unlike in macro-hardness that is measured according to geometric similarity of individual dints).
winter, he passed the time analyzing and correlating hardness data with bulk modulus and shear modulus values, he recalls.
The grains themselves have a hardness of 2800 kg/[mm.
Electronic apparatus is intended to hardness determination of metals and alloys in field and laboratory conditions using a portable manual structure with aid of the material is tested by a diamond indenter, hardness being expressed by its resistance to indenter action.
While hardness variations can occur in aluminum castings, it is unusual to see such a dramatic variation within the same part.
Indentation hardness refers to resistance to deformation by a loaded indenter, usually one with a shaped tip (pyramid, hemisphere, or wedge) such that the contact area increases with increased indentation.
Hardness was determined by loading 200 micronewton force.
Indentation or hardness testing has long been used for characterization and quality control of materials, but the results are not absolute and depend on the test method.
What: Durometer hardness testers for plastic and rubber parts producers
To a metallurgist, hardness is a material's resistance to penetration.