**OBLIQUE - **Straight line that makes the horizontal or other straight an angle from the range 0 to 180º but different from 90º.

**OBTUSE** - An angle that measures over 90 degrees but less than 180 degrees.

**OCTAEDRO - **Eight-sided polyhedron.

**OCTAGON** - Polygon that has eight sides and eight angles.

**OCTANT - **Each of the 8 portions of space determined by the 3 coordinate planes.

**ORDER **- Ordered arrangement that can be in ascending or descending order. There is a pattern of behavior for objects.

**ASCENDING ORDER** - Arrangement of a group of numbers in order, so that a smaller number is always placed before a larger one. Example: 3, 6, 9, 12, 27.

**DESCENDING ORDER** - Arrange a group of numbers in order so that a larger number is placed before a smaller one. Example: 27, 12, 9, 6, 3.

**ORDERED **- See coordinates.

**ORDINAL -** Word that indicates the order of placement in a set of one of its objects (1st, 2nd, 3rd,â€¦) or (first, second, thirdâ€¦).

A - B - C - D - E - F - G - H - I / J / K - L - M - N - O - P - Q - R - S - T - U / V - X / Z