**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.

© Webster 1913.

**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.

⇒ 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.

© Webster 1913.