normal

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Conforming with, adhering to, or constituting a norm, standard, pattern, level, or type; typical.
• adjective Biology Functioning or occurring in a natural way; lacking observable abnormalities or deficiencies.
• adjective Relating to or designating the normality of a solution.
• adjective Designating an aliphatic hydrocarbon having an acyclic unbranched chain of carbon atoms.
• adjective Being at right angles; perpendicular.
• adjective Perpendicular to the direction of a tangent line to a curve or a tangent plane to a surface.
• adjective Relating to or characterized by average intelligence or development.
• adjective Free from mental illness; sane.
• noun The usual, expected, or standard state, form, amount, or degree.
• noun Mathematics A perpendicular, especially a perpendicular to a line tangent to a plane curve or to a plane tangent to a space curve.

from The Century Dictionary.

• According to a rule, principle, or norm; conforming to established law, order, habit, or usage; conforming with a certain type or standard; not abnormal; regular; natural.
• Serving to fix a standard; intended to set the standard: as, a normal school (see below).
• In music, standard or typical: as, normal pitch or tone, a pitch or tone of absolute acoustical value, which is used as a standard of comparison. See key, 7, and natural key (under key).
• In geometry, perpendicular: noting the position of a straight line drawn at right angles to the tangent-line of a curve, or to the tangent-plane of a surface, at the point of contact.
• Synonyms Regular, Ordinary, Normal. That which is regular conforms to rule or habit, and is opposed to that which is irregular, fitful, or exceptional. That which is ordinary is of the usual sort and excites no surprise; it is opposed to the uncommon or the extraordinary. That which is normal conforms or may be figuratively viewed as conforming to nature or the principles of its own constitution: as, the normal action of the heart; the normal operation of social influences; the normal state of the market.
• noun In geometry, a perpendicular; the straight line drawn from any point in a curve in its plane at right angles to the tangent at that point; or the straight line drawn from any point in a surface at right angles to the tangent-plane at that point. See cut under binomial.
• In chem.:
• Of a salt, having all the readily replaceable or basic hydrogen of the corresponding acid replaced by one or more metals or strongly electropositive radicals: distinguished from an acid salt in which this replacement is only partial.
• Of a solution for use in volumetric analysis, containing of the dissolved chemical substance the reactive equivalent of 1 gram of hydrogen in 1 liter of the solution at 16° C. See normal solution.
• noun The rule; the standard.
• noun In biology, a species or race considered as a fixed standard which individual organisms may approach by heredity and from which they may recede by variation.
• noun In meteorology, the average of a large number of observed values of any given meteorological element, for example, mean temperature, pressure, or rainfall for any hour of the day, or day of the year. The number of observations must be so large that a second group of the same number would give the same average or normal. The normals for the hours of local mean solar time may be corrected or adjusted so as to become normals for the hours of any other standard of time.
• noun In compar. psychol., an untrained or uninjured animal whose behavior is made the standard of reference for the interpretation of the conduct of other, trained or operated animals.

from the GNU version of the Collaborative International Dictionary of English.

• adjective 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.
• adjective (Geom.) According to a square or rule; perpendicular; forming a right angle. Specifically: Of or pertaining to a normal.
• adjective (Chem.) Standard; original; exact; typical.
• adjective (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.
• adjective (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.
• adjective (Organ. Chem.) Denoting that series of hydrocarbons in which no carbon atom is bound to more than two other carbon atoms; Cf. Iso-.
• adjective (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.
• adjective (Geol.) a group of rocks taken as a standard.
• adjective (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.
• adjective a school whose methods of instruction are to serve as a model for imitation; an institution for the training of teachers.
• noun (Geom.) Any perpendicular.
• noun (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective According to norms or rules.
• adjective Usual; ordinary
• adjective Healthy; not sick or ill
• adjective Pertaining to a school to teach teachers how to teach.
• adjective chemistry of, relating to, or being a solution containing one equivalent weight of solute per litre of solution.
• adjective organic chemistry Describing a straight chain isomer of an aliphatic hydrocarbon, or an aliphatic compound in which a substituent is in the 1- position of such a hydrocarbon
• adjective physics (Of a mode in an oscillating system) In which all parts of an object vibrate at the same frequency; See normal mode
• adjective geometry Perpendicular to a tangent line or derivative of a surface in Euclidean space.
• adjective algebra (Of a subgroup) whose cosets form a group
• adjective algebra (Of a field extension of a field K) which is the splitting field of a family of polynomials in K
• adjective probability theory, statistics (Of a distribution) which has a very specific bell curve shape
• adjective complex analysis (Of a family of continuous functions) which is pre-compact