what is the definition of density, and what are three different units for density?

Answer 1

http://www.just-define.com/density-definition.htm

Definition of density

density
n 1: the amount per unit size [syn: denseness]
2: the spatial property of being crowded together [syn: concentration,
denseness, compactness] [ant: distribution]

As defined in: WordNet (r) 2.0
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Density \Den"si*ty\, n. [L. densitas; cf. F. densit['e].]
1. The quality of being dense, close, or thick; compactness;
-- opposed to rarity.

2. (Physics) The ratio of mass, or quantity of matter, to
bulk or volume, esp. as compared with the mass and volume
of a portion of some substance used as a standard.

Note: For gases the standard substance is hydrogen, at a
temperature of 0[deg] Centigrade and a pressure of 760
millimeters. For liquids and solids the standard is
water at a temperature of 4[deg] Centigrade. The
density of solids and liquids is usually called
specific gravity, and the same is true of gases when
referred to air as a standard.

3. (Photog.) Depth of shade. --Abney.

As defined in: Webster's Revised Unabridged Dictionary (1913)
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Density \Den"si*ty\ (d[e^]n"s[i^]*t[y^]), n. [L. densitas; cf.
F. densit['e].]
1. The quality of being dense, close, or thick; compactness;
-- opposed to rarity.
[1913 Webster]

2. (Physics) The ratio of mass, or quantity of matter, to
bulk or volume, esp. as compared with the mass and volume
of a portion of some substance used as a standard.
[1913 Webster]

Note: For gases the standard substance is hydrogen, at a
temperature of 0[deg] Centigrade and a pressure of 760
millimeters. For liquids and solids the standard is
water at a temperature of 4[deg] Centigrade. The
density of solids and liquids is usually called
specific gravity, and the same is true of gases when
referred to air as a standard.
[1913 Webster]

3. (Photog.) Depth of shade. --Abney.
[1913 Webster]

As defined in: English Monolingual Dictionaries
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71 Moby Thesaurus words for "density":
asininity, blockishness, body, boobishness, boorishness, bovinity,
callosity, callousness, cloddishness, concreteness, crassness,
crudeness, denseness, dim-wittedness, dimness, doltishness,
dull-wittedness, dullardism, dullness, dumbness, duncery,
durability, durity, firmness, flintiness, grossness, hardness,
hardness of heart, hebetude, impenetrability, induration, lethargy,
loutishness, lumpishness, mass, materiality, ninnyism, oafdom,
oafishness, obduracy, obtuseness, opacity, palpability,
ponderability, resistance, restiveness, simpletonianism, slowness,
sluggishness, solidity, sottishness, soundness, stability,
steadiness, steeliness, stolidity, stoniness, stoutness, strength,
stupidity, sturdiness, substance, substantiality, substantialness,
tangibility, thick-headedness, thick-wittedness, toughness,
unteachability, wrongheadedness, yokelism




As defined in: Moby Thesaurus II by Grady Ward, 1.0

Answer 2

The mass per unit volume of a material. The term is applicable to mixtures and pure substances and to matter in the solid, liquid, gaseous, or plasma state.

Density of all matter depends on temperature; the density of a mixture may depend on its composition, and the density of a gas on its pressure.

Common units of density are grams per cubic centimeter, and slugs or pounds per cubic foot.

The specific gravity of a material is defined as the ratio of its density to the density of some standard material, such as water at a specified temperature, for example, 60°F (15.6°C), or, for gases the basis may be air at standard temperature and pressure.

Another related concept is weight density, which is defined as the weight of a unit volume of the material.

Answer 3

Ratio of unit mass and unit volume.1 g of pure water has 1 cubic centimetre of volume which is 1 g/cc .
kg/cm3 and lb/cu in (psi) are also density units.
Density is actually a comparison of mass with same volume or comparison of volume with same mass.

Answer 4

density = mass / volume

As for units, just put any mass over any volume... for example

kg / inches^3

lbs / km^3

kg / nm^3