# Online Math Dictionary: F

Easy to understand math definitions for K-Algebra mathematics
Just scroll down or click on the word you want and I'll scroll down for you!

 face of a polyhedron factor in arithmetic factor in algebra factorial Fibonacci numbers finite formula fractal fraction function

 Face of a PolyhedronA face of a polyhedron is one of the sides. Example:  In the dodecahedron on the right, we can see one green face, one purple face, two red facesand two blue faces.  (There are six more faces on the back side that we can't see.) For  more info on polyhedra, check out myPolyhedra Gallery.  Factor in Arithmetic
A factor in arithmetic is one of the two or three (or more) things we multiply together to get our answer.  In the examples below, the factors are the blueand red numbers.
Examples:    6  2 x 3        120 = 4 x 5 x 6
For more info, check out my Multiplication Lessons. Factor in Algebra
Factors in Algebra are the same thing as factors in arithmetic... Factors are the things we multiply together to get answers.  In the example below, the factors are in red and blue. For some great lessons on factoring, check out my factoring lessons. FactorialHere's the official formula for a factorial:     n! = n x (n-1) x (n-2) x ... x 3 x 2 x 1 It looks creepy, but it isn't.Example:   4! = 4 x 3 x 2 x 1 = 24         5! = 5 x 4 x 3 x 2 x 1 = 120     3! = 3  x 2 x 1 0! is specially defined as:  0! = 1For more info on factorials, check out my factorials lesson.

Fibonacci numbers
The Fibonacci numbers are a sequence (list) of numbers that is built a very special way...   It starts with  1, 1...  Then, you add 1+1 to get the next number...  That gives 1, 1, 2...  Then you add 1+2 to get the next number...  That gives  1, 1, 2, 3...  Then you add 2+3 to get the next number...  That gives 1, 1, 2, 3, 5...  Then you add3+5 to get the next number...
That gives 1, 1, 2, 3, 5, 8...  and you keep going!
1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
Sometimes, people start the list with 0, 1...  But, check it and you'll see that you get the same thing. Finite
Finite means that there is an end to the thing you are counting.
Here is a finite sequence of numbers:  5, 6, 7, 8 Formula
Formulas are rules and sentences in math that are just written in math language instead of words.  One of the most famous formulas is Einstein's energy formula: where E is energym is the mass of a body and c is the speed of light FractalA fractal is an image or mathematical pattern that is generated by a computer using complex numbers. It sounds crazy, but lots of natural objects like snowflakes, crystals, and leaves have these fractal patterns inside of them!  FractionA fraction is a way to count PART of something - like part of a pizza instead of the whole thing.  A fraction is made up of a numerator (on the top) and a denominator (on the bottom.) For more info on fractions, check out my fraction lessons.  FunctionA function is a rule in Algebra that's like a box (see pic on the right) where you put something in (called a domain element) and something comes out (called a range element).  Officially, a rule (or relation) is a function if, for every domain element that goes in,EXACTLY one range element comes out. Here's an example of a function: To learn more about functions, check out my function lessons. A B C D E F G H I no J's K L M N O P Q R S T U V W no X's no Y's no Z's