A dodecahedron is a polyhedron with twelve flat faces. The most common type is the regular dodecahedron made up of 12 regular pentagons, which is one of the five Platonic solids.

Volume refers to the amount of space inside a container that can hold objects. It's commonly used to describe how much a box, oil drum, bottle, etc., can hold. When calculating, you need to use the internal dimensions, and the usual units are liters and milliliters.

A pentadecagon is a flat polygon with 15 sides and 15 angles, and the sum of its interior angles is fixed at 2340 degrees.

An acute angle is an angle that is greater than 0° but less than 90°.

A hendecagon is a flat shape with 11 sides and 11 angles, and it’s a type of polygon.

An acute triangle is a triangle where all three interior angles are less than 90 degrees. It's one type of triangle based on angles, the other two being right triangles and obtuse triangles.

An hour is the internationally used unit of time, and 1 hour equals 60 minutes or 3600 seconds.

Trigonometry is a tool in math used to describe the relationship between angles and side lengths. The most common ones are sine, cosine, and tangent, which can turn angles into actual numbers and are widely used in physics, engineering, and construction calculations.

The concept of time includes moments and periods. Time is a parameter humans use to describe the process of material movement or the occurrence of events.

It's a closed shape made by connecting three line segments end to end in the same plane, as long as they're not on the same line. It's a basic geometric figure.