340 Appendix C
ordered pair Two numbers, usually designated as x and y, that locate a point in a coordinate
system.
order of operations An agreement among mathematicians that we perform operations
enclosed in parentheses or other grouping symbols first and then evaluate exponents. After that,
do multiplication and division as you meet them moving left to right, and finally do addition and
subtraction as you meet them, moving left to right.
parallel lines Lines on the same plane that never intersect.
parallelogram A quadrilateral in which both pairs of opposite sides are parallel.
PEMDAS A mnemonic, or memory device, to help you remember that the order of operations
is parentheses, exponents, multiplication and division, addition, and subtraction.
percent A ratio that compares numbers to 100. 42% means 42 out of 100, or 42:100.
perimeter The total of the lengths of all the sides of a polygon.
period A group of three digits in a large number. The ones, tens, and hundreds form the ones
period. The next three digits are the thousands period, then the millions, the billions, trillions,
and on and on.
permutation An arrangement or ordering of a group of objects.
perpendicular lines Lines that meet to form a right angle.
place value system A number system in which the value of a symbol depends on where it is
placed in a string of symbols.
plane A f lat surface that has length and width but no thickness.
point A position in space that has no length, width, or height.
polygon A closed figure made up of line segments that meet at their endpoints.
polyhedron A solid constructed from polygons that meet at their edges.
polynomial An expression formed by adding terms, each of which is a number times a power of
a variable.
power of ten A number formed by multiplying several 10s. The first power of ten is 10. The
second power of ten is 100, and the third power of 10 is 1,000.
prime factorization The prime factorization of a number is a multiplication that uses only
prime numbers and produces the original number as its product.
prime number A prime number is a whole number whose only factors are itself and 1.