Geometry Glossary - S

Scale drawings:

pictures of real-life objects rendered in smaller than life-size (or larger) dimensions, with relative sizes maintained

Scalene triangle:

a triangle with no sides congruent

Secant of a circle:

a line that intersects a circle in two points

Sector of a circle:

a region in a circle bounded by a central angle and the arc it cuts

Segment:

"a piece of a line"; the union of two distinct points (called endpoints) and all the points between them

Septagon:

a seven-sided polygon

 

 

 

Sides (of a triangle):

three segments which meet at their endpoints to enclose a triangular region

Similar polygons:

polygons whose corresponding sides have proportional measures, and whose corresponding angles have equal measure

Simple closed curves:

a closed plane figure that does not intersect itself

Sine:

a trigonometric function equal to the y-coordinate of the point of intersection of the terminal ray of an angle in standard position with the unit circle

Sketch:

a rough, quickly done drawing, painting, clay model, or design

Skew lines:

two lines which do not intersect and cannot be contained in the same plane

Slant height of a cone:

a segment that joins the tip of a cone to the edge of its base; the slant height is also the radius of the sector that forms the lateral surface

Slant height of a pyramid:

a segment that joins the tip of a pyramid to the midpoint of a side of its base; the slant height is the actual height of the triangular face and is essential for finding lateral surface area

Slope:

the pitch, or slant, of a line. In the coordinate plane, slope is defined as the change in the y-coordinates divided by the change in x-coordinates

Slope-intercept form of a linear equation:

 y=mx+b, where m is the slope and b is the y-intercept

Solid:

the union of a surface and the space it encloses

Space:

the union of all points

Sphere:

the set of all points that are a given distance (the radius) from a fixed point (the center)

Square:

a quadrilateral with four right angles and four equal sides

Standard form of a quadratic equation:

 ax² + bx + c = 0

Standard position:

an angle is in standard position if its initial ray is the x-axis

Straightedge:

a strip of plastic, wood, or metal having one edge accurately straight, used in drawing or testing straight lines and level surfaces; a ruler is often used as a straightedge for drawing

 

Sufficient (in conjunction with "necessary"):

being as much as is needed, adequate

Supplementary angles:

two angles whose measures total 180 degrees; one angle is said to be the "supplement" of the other

Surface:

the polygonal or smooth regions that meet at their edges to enclose space; a surface can be represented by a two-dimensional net

Surface area:

the sum of the area of the faces (or smooth surfaces) of a solid; it is the area of the net which covers the solid

Symmetric figures:

figures may have symmetry, which may be bilateral symmetry (the figure could be folded on an imaginary line and match itself on each side of the line), or rotational symmetry (the figure could be rotated to match itself, such as a pentagon); separate figures, which could be flipped or rotated to coincide with each other are also called symmetric

Synthetic geometry:

created from postulates and other factitious constructs (such as from straight edge and compass constructions); in synthetic geometry, equations and numbers are not used to describe figures, thus making it different from analytic geometry and coordinate representations (Euclidean geometry is one type of synthetic geometry)

Synthetic proof:

in this context, a proof using the theorems and postulates that mathematicians have created for Euclidean geometry; this differs from analytic geometry proofs, which would use algebraic constructs, or transformational proofs