12 terms

parallel lines

Two or more lines which are the same distance apart and will never touch. Railroad tracks are an example of parallel lines. Also the l's in the word parallel are an example.

perpendicular lines

Two or more lines which intersect (cross) to make right angles (square corners). Think of a plus sign and uppercase or lowercase T.

polygon

Any multi-sided closed figure.

quadrilateral

Any polygon with exactly four straight sides. Quad=four; lateral=line, so quadrilateral literally means "four lines".

parallelogram

A quadrilateral where both sets of opposite sides are parallel to each other, and it may or may not have square corners.

trapezoid

A quadrilateral that is not a parallelogram. Opposite sides are not always equal length and one or more corners are not square (right angles).

rectangle

A parallelogram which has four right angles (square corners) and opposite sides are equal to each other.

rhombus

A parallelogram which has four sides equal to each other, but may or may not have square corners.

square

Both a rectangle and a rhombus. All four sides are equal. All four corners are right angles (square corners).

line

A plane figure that continues forever in both directions. There are no endpoints.

line segment

A plane figure with two endpoints. A line segment can be measured.

point

An exact location on a line.