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The Collaborative International Dictionary of English v.0.48 (gcide)

Normal \Nor"mal\ (n[^o]r"mal), a. [L. normalis, fr. norma rule,
pattern, carpenter's square; prob. akin to noscere to know;
cf. Gr. gnw`rimos well known, gnw`mwn gnomon, also,
carpenter's square: cf. F. normal. See {Known}, and cf.
{Abnormal}, {Enormous}.]
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1. According to an established norm, rule, or principle;
conformed to a type, standard, or regular form; performing
the proper functions; not abnormal; regular; natural;
analogical.
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Deviations from the normal type. --Hallam.
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2. (Geom.) According to a square or rule; perpendicular;
forming a right angle; as, a line normal to the base.
Specifically: Of or pertaining to a normal.
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3. (Chem.) Standard; original; exact; typical. Specifically:
(a) (Quantitative Analysis) Denoting a solution of such
strength that every cubic centimeter contains the same
number of milligrams of the element in question as the
number of its molecular weight.
(b) (Chem.) Denoting certain hypothetical compounds, as
acids from which the real acids are obtained by
dehydration; thus, normal sulphuric acid and normal
nitric acid are respectively {S(OH)6}, and {N(OH)5}.
(c) (Organ. Chem.) Denoting that series of hydrocarbons in
which no carbon atom is bound to more than two other
carbon atoms; as, normal pentane, hexane, etc. Cf.
{Iso-}.
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{Normal equations} (Method of Least Squares), a set of
equations of the first degree equal in number to the
number of unknown quantities, and derived from the
observations by a specified process. The solution of the
normal equations gives the most probable values of the
unknown quantities.

{Normal group} (Geol.), a group of rocks taken as a standard.
--Lyell.

{Normal place} (of a planet or comet) (Astron.), the apparent
place in the heavens of a planet or comet at a specified
time, the place having been determined by a considerable
number of observations, extending perhaps over many days,
and so combined that the accidental errors of observation
have largely balanced each other.

{Normal school}, a school whose methods of instruction are to
serve as a model for imitation; an institution for the
training of teachers.
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Syn: {Normal}, {Regular}, {Ordinary}.

Usage: Regular and ordinary are popular terms of well-known
signification; normal has now a more specific sense,
arising out of its use in science. A thing is normal,
or in its normal state, when strictly conformed to
those principles of its constitution which mark its
species or to the standard of a healthy and natural
condition. It is {abnormal} when it departs from those
principles.
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Normal \Nor"mal\ (n[^o]r"mal), n. [Cf. F. normale, ligne
normale. See {Normal}, a.]
1. (Geom.) Any perpendicular.
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2. (Geom.) A straight line or plane drawn from any point of a
curve or surface so as to be perpendicular to the curve or
surface at that point.
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Note: The term normal is also used to denote the distance
along the normal line from the curve to the axis of
abscissas or to the center of curvature.
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