# normal

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Related to normally: Normally distributed

## Normal

Normal, town (1990 pop. 40,023), McLean co., central Ill.; inc. 1865. It is the center of a productive farming region. Motor vehicles are manufactured in Normal. The town originally grew around Illinois State Univ. (1857; formerly called Illinois State Normal Univ.), which remains a major contributor to its economy.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Normal

(to a curve or surface). The normal at a given point of a curve or surface is a line that passes through this point and is perpendicular to the tangent line or tangent plane at the same point of the curve or surface. A plane curve has at each point a single normal that lies in the plane of the curve. If x = f(t) and y = g(t) are parametric equations of a plane curve L, then the equation of the normal at point (x0, y0) of curve L that corresponds to the value to of the parameter; may be written as

For a plane curve defined by the equation F(x,y) = 0, the equation of the normal has the form

A space curve has at each point an infinite set of normals, and these normals all lie in a certain plane (the normal plane). The normal that lies in the osculating plane is called the principal normal. The normal that is perpendicular to the osculating plane is called the binormal. The tangent, the principal normal, and the binormal form the moving trihedral of the curve.

For the surface defined by the equation F(x, y, z) = 0, the normal can be represented by the equations

The concept of the normal plays a significant role not only in differential geometry but also in various applications of this subject, such as geometrical optics and mechanics. The formulation of the fundamental laws of refraction and reflection of light rays is an example from geometrical optics; in mechanics, a mass point or a physical body experiences a reaction directed along the normal when it is displaced along smooth curves or surfaces; in a conservative field, the lines of force at each point are directed along the normal to the isopotential surface that passes through the point.

## normal

[′nȯr·məl]
(meteorology)
The average value of a meteorological element over any fixed period of years that is recognized as standard for the country and element concerned.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

## normal

i. As it pertains to meteorology, the value of an element averaged for a given location over a period of time, normally fifty years, and recognized as a standard.
ii. Equivalent to usual, regular, rational, or standard conditions.
iii. At a right angle to the datum under reference.

## normal

1. Psychol
a. being within certain limits of intelligence, educational success or ability, etc.
b. conforming to the conventions of one's group
2. Biology Med (of laboratory animals) maintained in a natural state for purposes of comparison with animals treated with drugs, etc.
3. Chem (of a solution) containing a number of grams equal to the equivalent weight of the solute in each litre of solvent.
4. Chem denoting a straight-chain hydrocarbon: a normal alkane. Prefix: n-, e.g. n-octane
5. Geometry another word for perpendicular
6. Geometry a line or plane perpendicular to another line or plane or to the tangent of a curved line or plane at the point of contact
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Moray: Stag scatter cushion - [euro]25 (normally [euro]39)
Residents whose bins are normally collected on Tuesdays will have their rubbish taken away on Wednesday and so on.
"Ports are operating normally, and there are no problems," he added.
If he normally makes the first move, just start innocently touching him instead.
All told, from the phone call to the CM to the case decision, a CAP appeal can take a minimum of 10 business days (effectively, two weeks), and normally takes a maximum of 15.
If the appraiser is valuing 100% of the casting facility, a control premium, which is the increase in value normally paid to obtain control, must be applied.
These results suggest that DJ-1 normally protects against oxidative stress and that its inactivation may leave neurons susceptible to oxidative damage.
At birth, people normally have in place basic nerve structures with the potential to grow into an efficient signal-relaying operation.
For example, if a trust sells real estate for a \$1,025,000 gain before \$50,000 of sales costs and commissions--and the trust also has \$75,000 of rental income with \$50,000 of related expenses--the \$1 million net economic benefit normally would be allocated \$975,000 to principal and \$25,000 to income.
Surgery as complicated as that performed on Kadhem is normally done in a series of operations, but because the boy had to return to Iraq, Dr.
The alarm lights the red detect lamp on the front panel, it also closes a normally open relay contact closure to signal the detection event.
"Normally there are two pump elements that provide the active pressure build up, but with CAPS we have six pump elements--three for each circuit.

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