This is a super-cool dictionary.

A few short interesting entries:

*“It is common in mathematics now to use the Halmos symbol to indicate the end of a proof. It is named for mathematician Paul Halmos who seems to have first applied it to mathematics. Halmos has stated that he got the symbol from popular magazines where it was used to indicate the end of an article. It is also frequently called the tombstone.”*

*“The symbol “÷” which is used to indicate the operation of division is called an obelus… By a misunderstanding of a credit to John Pell about other material in the book, many English writers started using the symbol and calling it “Pell’s notations”. It is one of the most territorial of all math symbols, appearing in regular use in both the US and Great Britain and yet nearly non-existant in the rest of the world.”*

*“The latin word for the greek term ortho, was rectus which was also used to mean both straight and erect. We see the imprint of rectus in many math words and common language with both the straight and erect meanings. The rectum is so called because it is the “straight intestine”, while a rectangle is a parallelogram with an “erect angle”. In fact, the word rectangle was sometimes used for a “right angle” into the 19th century.*

*The latus rectum in a parabola is the side (latus) through the focus that is straight (rectus – parallel to the directrix). Latus rectum is the Latin translation of the Greek orthea pleura for erect side which was the term Apollonius used in his books on the conic sections. As languages blended in the middle ages, rectos became “recht” and eventually became our word for “right” and for the right angle.”*

*“A mathematician named Klein *

* Thought the Mobius strip was divine *

* He said “If you glue *

* The edges of two *

* You can make a strange bottle like mine”.”*

*“Q: Why did the chicken cross the Möbius strip?*

* A: To get to the same side.”*

*“The shortest path between two points on the surface of the Earth is along a great circle arc, but this path is often not possible for ships. One reason is that a great circle arc takes constant changes of compass heading. Because it is not much longer in the middle latitudes, ships often sail a path of constant compass heading, called a loxodrome.”*

Also, statistician Karl Pearson is a badass.

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