Short for Operating System. The main software that manages your computer’s hardware and software.

An octagon is a closed shape formed by eight line segments, with an interior angle sum of 1080 degrees. It can be a regular octagon or an irregular octagon and is often used in architecture and signage design.

An octagon is a closed shape made up of eight line segments, with a total interior angle of 1080 degrees. It can be a regular octagon or an irregular one, and in everyday life, it’s often used in architecture and sign design.

The octahedron is actually a big family; any polyhedron made up of eight faces is called an octahedron. But the one people usually talk about is the most regular one, the 'regular octahedron.' A regular octahedron is made up of 8 congruent equilateral triangles, has 6 vertices and 12 edges, and looks like two square pyramids joined at their bases.

Symmetry order (also called symmetry number) refers to the minimum number of times an object or system coincides with itself under operations like rotation, translation, or interval changes. It's usually denoted as n, corresponding to n-fold symmetry.

An obtuse angle in math refers to an angle that is greater than 90° but less than 180°. For example, putting together two 45° acute angles can make an obtuse angle. This is a basic concept in learning geometry.

An obtuse triangle is a triangle that has one obtuse angle, meaning this angle is greater than 90 degrees but less than 180 degrees.

Besides the basic arithmetic and geometric sequences, math also has all kinds of special sequences and broader concepts that follow specific patterns or have important applications.

An oblique triangle is a triangle that doesn't have a right angle, including both acute and obtuse types.

In the field of professional mathematics, it refers to the process of calculating the best solution under constraints.