# 2020 Top Ten of Polemic for Mathematics

- Nice name
- In set theory, a nice name is used in forcing to impose an upper bound on the number of subsets in the generic model. It is used in the context of forcing to prove independence results in set theory such as Easton's theorem
- Scale factor
- A scale factor is usually a decimal which scales, or multiplies, some quantity. In the equation y = Cx, C is the scale factor for x. C is also the coefficient of x, and may be called the constant of proportionality of y to x. For example, doubling distances corresponds to a scale factor of two for distance, while cutting a cake in half results in pieces with a scale factor for volume of one half. The basic equation for it is image over preimage
- Like terms
- In algebra, like terms are terms that have the same variables and powers. The coefficients do not need to match
- Perpendicular
- In elementary geometry, two geometric objects are perpendicular if they intersect at a right angle
- Circumference
- In geometry, the circumference is the perimeter of a circle or ellipse. That is, the circumference would be the arc length of the circle, as if it were opened up and straightened out to a line segment. More generally, the perimeter is the curve length around any closed figure.
Circumference may also refer to the circle itself, that is, the locus corresponding to the edge of a disk.
The circumference of a sphere is the circumference, or length, of any one of its great circles
- Tree diagram (probability theory)
- In probability theory, a tree diagram may be used to represent a probability space
- 4000 (number)
- 4000 is the natural number following 3999 and preceding 4001. It is a decagonal number
- Clock angle problem
- Clock angle problems are a type of mathematical problem which involve finding the angle between the hands of an analog clock
- Composite number
- A composite number is a positive integer that can be formed by multiplying two smaller positive integers. Equivalently, it is a positive integer that has at least one divisor other than 1 and itself. Every positive integer is composite, prime, or the unit 1, so the composite numbers are exactly the numbers that are not prime and not a unit
- Table of prime factors
- The tables contain the prime factorization of the natural numbers from 1 to 1000