**nor·mal** [nawr-muh

l] Show IPA

adjective 1. conforming to the standard or the common type; usual; not abnormal; regular; natural.

2. serving to establish a standard.

3. Psychology . a. approximately average in any psychological trait, as intelligence, personality, or emotional adjustment.

b. free from any mental disorder; sane.

4. Biology, Medicine/Medical . a. free from any infection or other form of disease or malformation, or from experimental therapy or manipulation.

b. of natural occurrence.

5. Mathematics . a. being at right angles, as a

line; perpendicular.

b. of the

nature of or pertaining to a mathematical normal.

c. (of an orthogonal system of real functions) defined so that the integral of the square of the

absolute value of any function is 1.

d. (of a topological space) having the property that corresponding to every pair of disjoint closed sets are two disjoint open sets, each containing one of the closed sets.

e. (of a subgroup) having the property that the same

set of elements results when all the elements of the subgroup are operated on consistently on the left and consistently on the right by any element of the group; invariant.

noun 7. the average or

mean: Production may fall below normal.

8. the standard or type.

9. Mathematics . a. a perpendicular line or plane, especially one perpendicular to a tangent line of a curve, or a tangent plane of a surface, at the point of contact.

b. the portion of this perpendicular line included between its point of contact with the curve and the x- axis.