O
Obtuse angle An
angle with measure between 90°
and 180°.
Obtuse triangle A
triangle that has one obtuse angle.
Odds A ratio that compares the probability of an event occurring and
the probability of the event not occurring.
Open sentence A
mathematical sentence that contains one or more variables.
opposite
of such a fraction.
Opposites A pair
of numbers such as - and .
Order
of operations The rules
stating the order to follow in working a problem containing several different
operations
Ordered pair of numbers A
pair of numbers whose order is important.
Ordering
Arranging
a set of numbers in a list so that each number is less than the numbers that
come after it in the
list
and greater than the numbers that come before it
Origin ,
The graph of zero on a number line or in a rectangular coordinate plane.
Outcome The result of an event.