A fork of Rural Dictionary
A sigma algebra (or σ-algebra) is to set algebras what sigma males are to males. The Borel hierarchy (the analog of the male hierarchy) is not a σ-algebra at any countable rank; instead the σ-algebra has the largest possible rank -- ω_1, the least uncountable ordinal (under suitable conditions e.g. the Polish space is uncountable. This is known as the non-collapse of the Borel hierarchy). A σ-algebra is closed under countable union, countable intersection, and relative complement. This means σ-algebras arise naturally in the study of measure theory, where the measurable sets form a σ-algebra.
The algebra of Lebesgue-measurable subsets of R (i.e. the sets of real numbers with a well-defined "length", which is possibly infinity) form a sigma algebra.
The one phrase created by kareem the stinky man, use this if you don’t want to make friends. Use this if you want to be hated
you smell like Pre algebra
One of the useless forms of math. Comes before Algebra, which is both useless
Nerd: Hey, do you want to know what 5/0.2 of 67.82³ Jock: I hate you. And Pre-Algebra Nerd: 7798541.0942 (Yes this is true) Jock: Wait, why did you say that last part so quietly? Nerd: ....