Risk analysis is a systematic process of identifying, assessing, and managing potential risk factors. Its main parts include risk assessment, risk management, and risk information communication.

The common denominator is the same denominator that several fractions with different denominators are converted to when finding a common denominator; essentially, it's a common multiple of the denominators.

Closure mainly refers to the property of a set where, after performing a certain operation, the result still stays within the set. It's a basic concept in math and computer science.

A public key is a type of key in asymmetric key encryption algorithms. It comes with a unique pair of a public key and a private key. The public key can be shared openly and is used to encrypt data or verify digital signatures, while the private key is kept secret by the user and is used for decryption or signing.

Looking down from a high place is often used to describe observing things below from above, like when a house is built on a small hill overlooking a river.

In math class, when solving a quadratic equation, you can directly plug the coefficients into the quadratic formula to get the result. This method is called the formula method and is where many people first encounter formulas. But the meaning of a formula goes far beyond that; it's a universal tool for expressing patterns and simplifying calculations across different fields. Whether in scientific computations or everyday office work, you can see formulas in action.

Negative correlation refers to the phenomenon where two variables move in opposite directions—when one goes up, the other goes down.

The metric system, also known as the meter system, is an internationally used measurement system based on decimal units and is also the foundation of the modern International System of Units (SI).

It's a unit that represents the ratio of sound intensity or electrical signal power, usually shown as dB. It's mainly used to measure how loud or soft a sound is.

A icosahedron is a type of symmetrical polyhedron with 20 faces, 12 vertices, and 30 edges, where each face is an equilateral triangle, and it's one of the five Platonic solids.