Nor"mal (?), n. [Cf. F. normale, ligne normale. See Normal, a.]
1. (Geom.) Any perpendicular.
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.
&fist; 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.
Nor"mal (?), a. [L. normalis, fr. norma
rule, pattern, carpenter's square; prob. akin to noscere to know; cf. Gr. &?; well known, &?; gnomon, also, carpenter's square: cf. F.
normal. See Known, and cf. Abnormal, Enormous.]
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.
Deviations from the normal type.
Hallam. 2. (Geom.) According to a square or rule; perpendicular; forming a right angle. Specifically: Of or pertaining to a
normal.
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 united with more than two other carbon atoms; as, normal pentane, hexane, etc. Cf.
Iso-.
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.
Syn. -- Normal, Regular,
Ordinary. 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.
Hear it pronounced