Absolute
Value 
The
distance of a number from zero on a number line. Since distance
is always thought of as positive, the absolute value of any
number is always positive. 
Acute
Angle 
All
angles whose measures are between 0 and 90 degrees. 
Angle

A
figure formed by two rays that share the same endpoint. 
Angle
of Depression 
The
angle formed between a horizontal line and an oblique line joined
to some object below the horizontal. 
Angle
of Elevation 
The
angle formed between a horizontal line and an oblique line joined
to some object above the horizontal. 
Area 
The
number of square units required to cover a shape or figure. 
Axis
of Symmetry 
A
line, on which a figure can be folded, so that one side of the
figure will become superimposed over the other side of the figure. 