Unit \U"nit\, n. [Abbrev. from unity.]
1. A single thing or person.
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2. (Arith.) The least whole number; one.
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Units are the integral parts of any large number.
--I. Watts.
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3. A gold coin of the reign of James I., of the value of
twenty shillings. --Camden.
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4. Any determinate amount or quantity (as of length, time,
heat, value) adopted as a standard of measurement for
other amounts or quantities of the same kind.
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5. (Math.) A single thing, as a magnitude or number, regarded
as an undivided whole.
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Abstract unit, the unit of numeration; one taken in the
abstract; the number represented by 1. The term is used in
distinction from concrete, or determinate, unit, that is,
a unit in which the kind of thing is expressed; a unit of
measure or value; as 1 foot, 1 dollar, 1 pound, and the
like.
Complex unit (Theory of Numbers), an imaginary number of
the form a + broot-1, when a^2 + b^2 = 1.
Duodecimal unit, a unit in the scale of numbers increasing
or decreasing by twelves.
Fractional unit, the unit of a fraction; the reciprocal of
the denominator; thus, 1/4 is the unit of the fraction
3/4.
Integral unit, the unit of integral numbers, or 1.
Physical unit, a value or magnitude conventionally adopted
as a unit or standard in physical measurements. The
various physical units are usually based on given units of
length, mass, and time, and on the density or other
properties of some substance, for example, water. See
Dyne, Erg, Farad, Ohm, Poundal, etc.
Unit deme (Biol.), a unit of the inferior order or orders
of individuality.
Unit jar (Elec.), a small, insulated Leyden jar, placed
between the electrical machine and a larger jar or
battery, so as to announce, by its repeated discharges,
the amount of electricity passed into the larger jar.
Unit of heat (Physics), a determinate quantity of heat
adopted as a unit of measure; a thermal unit (see under
Thermal). Water is the substance generally employed, the
unit being one gram or one pound, and the temperature
interval one degree of the Centigrade or Fahrenheit scale.
When referred to the gram, it is called the gram degree.
The British unit of heat, or thermal unit, used by
engineers in England and in the United States, is the
quantity of heat necessary to raise one pound of pure
water at and near its temperature of greatest density
(39.1[deg] Fahr.) through one degree of the Fahrenheit
scale. --Rankine.
Unit of illumination, the light of a sperm candle burning
120 grains per hour. Standard gas, burning at the rate of
five cubic feet per hour, must have an illuminating power
equal to that of fourteen such candles.
Unit of measure (as of length, surface, volume, dry
measure, liquid measure, money, weight, time, and the
like), in general, a determinate quantity or magnitude of
the kind designated, taken as a standard of comparison for
others of the same kind, in assigning to them numerical
values, as 1 foot, 1 yard, 1 mile, 1 square foot, 1 square
yard, 1 cubic foot, 1 peck, 1 bushel, 1 gallon, 1 cent, 1
ounce, 1 pound, 1 hour, and the like; more specifically,
the fundamental unit adopted in any system of weights,
measures, or money, by which its several denominations are
regulated, and which is itself defined by comparison with
some known magnitude, either natural or empirical, as, in
the United States, the dollar for money, the pound
avoirdupois for weight, the yard for length, the gallon of
8.3389 pounds avoirdupois of water at 39.8[deg] Fahr.
(about 231 cubic inches) for liquid measure, etc.; in
Great Britain, the pound sterling, the pound troy, the
yard, or 1/108719 part of the length of a second's
pendulum at London, the gallon of 277.274 cubic inches,
etc.; in the metric system, the meter, the liter, the
gram, etc.
Unit of power. (Mach.) See Horse power.
Unit of resistance. (Elec.) See Resistance, n., 4, and
Ohm.
Unit of work (Physics), the amount of work done by a unit
force acting through a unit distance, or the amount
required to lift a unit weight through a unit distance
against gravitation. See Erg, Foot Pound,
Kilogrammeter.
Unit stress (Mech. Physics), stress per unit of area;
intensity of stress. It is expressed in ounces, pounds,
tons, etc., per square inch, square foot, or square yard,
etc., or in atmospheres, or inches of mercury or water, or
the like.
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Heat \Heat\ (h[=e]t), n. [OE. hete, h[ae]te, AS. h[=ae]tu,
h[=ae]to, fr. h[=a]t hot; akin to OHG. heizi heat, Dan. hede,
Sw. hetta. See Hot.]
1. A force in nature which is recognized in various effects,
but especially in the phenomena of fusion and evaporation,
and which, as manifested in fire, the sun's rays,
mechanical action, chemical combination, etc., becomes
directly known to us through the sense of feeling. In its
nature heat is a mode of motion, being in general a form
of molecular disturbance or vibration. It was formerly
supposed to be a subtile, imponderable fluid, to which was
given the name caloric.
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Note: As affecting the human body, heat produces different
sensations, which are called by different names, as
heat or sensible heat, warmth, cold, etc., according to
its degree or amount relatively to the normal
temperature of the body.
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2. The sensation caused by the force or influence of heat
when excessive, or above that which is normal to the human
body; the bodily feeling experienced on exposure to fire,
the sun's rays, etc.; the reverse of cold.
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3. High temperature, as distinguished from low temperature,
or cold; as, the heat of summer and the cold of winter;
heat of the skin or body in fever, etc.
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Else how had the world . . .
Avoided pinching cold and scorching heat! --Milton.
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4. Indication of high temperature; appearance, condition, or
color of a body, as indicating its temperature; redness;
high color; flush; degree of temperature to which
something is heated, as indicated by appearance,
condition, or otherwise.
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It has raised . . . heats in their faces. --Addison.
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The heats smiths take of their iron are a blood-red
heat, a white-flame heat, and a sparkling or welding
heat. --Moxon.
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5. A single complete operation of heating, as at a forge or
in a furnace; as, to make a horseshoe in a certain number
of heats.
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6. A violent action unintermitted; a single effort; a single
course in a race that consists of two or more courses; as,
he won two heats out of three.
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Many causes . . . for refreshment betwixt the heats.
--Dryden.
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[He] struck off at one heat the matchless tale of
"Tam o' Shanter." --J. C.
Shairp.
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7. Utmost violence; rage; vehemence; as, the heat of battle
or party. "The heat of their division." --Shak.
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8. Agitation of mind; inflammation or excitement;
exasperation. "The heat and hurry of his rage." --South.
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9. Animation, as in discourse; ardor; fervency; as, in the
heat of argument.
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With all the strength and heat of eloquence.
--Addison.
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10. (Zool.) Sexual excitement in animals; readiness for
sexual activity; estrus or rut.
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11. Fermentation.
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12. Strong psychological pressure, as in a police
investigation; as, when they turned up the heat, he took
it on the lam. [slang]
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Animal heat, Blood heat, Capacity for heat, etc. See
under Animal, Blood, etc.
Atomic heat (Chem.), the product obtained by multiplying
the atomic weight of any element by its specific heat. The
atomic heat of all solid elements is nearly a constant,
the mean value being 6.4.
Dynamical theory of heat, that theory of heat which assumes
it to be, not a peculiar kind of matter, but a peculiar
motion of the ultimate particles of matter.
Heat engine, any apparatus by which a heated substance, as
a heated fluid, is made to perform work by giving motion
to mechanism, as a hot-air engine, or a steam engine.
Heat producers. (Physiol.) See under Food.
Heat rays, a term formerly applied to the rays near the red
end of the spectrum, whether within or beyond the visible
spectrum.
Heat weight (Mech.), the product of any quantity of heat by
the mechanical equivalent of heat divided by the absolute
temperature; -- called also thermodynamic function, and
entropy.
Mechanical equivalent of heat. See under Equivalent.
Specific heat of a substance (at any temperature), the
number of units of heat required to raise the temperature
of a unit mass of the substance at that temperature one
degree.
Unit of heat, the quantity of heat required to raise, by
one degree, the temperature of a unit mass of water,
initially at a certain standard temperature. The
temperature usually employed is that of 0[deg] Centigrade,
or 32[deg] Fahrenheit.
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