scientific notation for large numbers A way of writing a large number in terms of a positive integer power of 10 multiplied by a number greater than or equal to 1 and less than 10.

scientific notation for small numbers A way of writing a small number in terms of a negative integer power of 10 multiplied by a number greater than or equal to1 and less than 10.

sector  A part of a circle bounded by two radii and the circle.

    .............___
segment ( AB )  The points A and B along
with the points on line
<--->
AB between A and B. Also called line segment.

semicircle  Half a circle.

short ton  A unit of weight in the U.S. system of measurement equal to 2,000 pounds.

side  One of the segments which makes up a polygon. One of the rays of an angle. One of the faces of a solid.

similar figures Two figures that have the same shape, but not necessarily the same size.

simple fraction  A fraction with an integer in the numerator and a nonzero integer in the denominator.

simpler number  A number used to more easily solve problems with complicated numbers.

size change factor  A number which multiplies other numbers to a change their size.

size change of magnitude k A transformation in which the coordinates of the original figure have all been multiplied by k.

Size Change Model for Multiplication   If a quantity x is multiplied by a size change factor k, then the result is a quantity k times as big.

slide image The result of adding the same number to the coordinates of the point in a figure. Also called translation image.

Slide Model for Addition  If a slide x is followed by a slide y, the result is a slide x + y.

Slide Model for Subtraction  If a quantity a is decreased by an amount b, the resulting quantity is a - b.

slope The name for the constant rate of change between two points on a line. The amount of change in the height of the line as you go 1 unit to the right. The slope of the line through (x1,y1) and (x2,y2) is
y2 - y1
x2 - x1

slope-intercept form An equation of a line in the form y = mx + b, where m is the slope and b is the y-intercept.

solution  A value of a variable that makes an open sentence true.

solving an open sentence  Finding values of the unknown ( s ) in an open sentence that make it true.

solving a proportion  Finding the value of a variable that makes a proportion true.

special case  An instance of a pattern used for some definite purpose.

sphere  The set of points in a space at a given distance from a given point.

square  A four-sided figure with four right angles and four sides of equal length. A rectangle with the same length and width.

square root  If A = s² , then s is called a square root of A.

square units  Units for measuring area.

straight angle An angle whose measures 180�.

Substitution Principle  If two numbers are equal, then one may be substituted for the other in any computation without changing the results of the computation.

subtrahend  b in the subtraction a - b.

sum The result of an addition.

supplementary angles  Two angles whose measures add to 180�.

surface area  The sum of the faces of a solid.

symmetric figure  A figure that coincides with its reflection image over a line. Also called line symmetry.

symmetry with respect to a line The property of a figure that coincides with its reflection image over a line. Also called line symmetry.

Take-away Model for Subtraction If a quantity y is taken away from an original quantity x with the same units, the quantity left is x - y.

tenth  A word name for 10^-1 or 0.1.

terminating decimal  A decimal that ends. Also called finite decimal.

terms  Numbers or expressions that are added or subtracted.

tessellation  A filling up of a two-dimensional space by congruent copies of a figure that do not overlap.

transformation  An operation on a geometric figure by which each point gives rise to a unique image.

translation image The result of adding the same numbers to the coordinates of the points in a figure. Also called slide image.

transversal A line that intersects two or more lines.

trapezoid A quadrilateral that has at least one pair of parallel sides.

trial and error  A problem-solving strategy in which various solutions are tried until the correct solution is found.

Triangle-Sum Property  In any triangle, the sum of the measures of the angles is 180�.

triangular region  A triangle and the space inside it.

trillion  A word name for 1,000,000,000,000.

trillionth A word name for 10^-12, or .000000000001.

truncate  To cut off a number at a particular decimal place.