There are hundreds of thousands of words in the English language, but not all of them are useful to everyone in everyday life. Many words are specific to a certain area of study or field of work; for example, if you’re not a geologist, you probably couldn’t define (and would never use) the words laccolith, horst, or oolite. We generally use the word terminology to describe words that are particular to any one field or study and which aren’t often used outside of that field. The word jargon means much the same thing, but more often refers to terminology that is confusing to outsiders, usually because it consists of acronyms, or words that are normal English words but used in a different way. A good example of this is in the area of computers, where an office worker might have no idea why the IT support person advised him to type in a URL where he could find a patch to fix the problem with his OCR.

Some words start out as jargon and later become part of the general language. As an example, look at the word tangential. The noun tangent was invented by a mathematician in the late 16th century to describe the point at which one line touches, but does not intersect (go through), another line. Today, we use these words in English conversation to refer to something that is only superficially or indirectly related to something else.

Example 1: According to the schedule, we were supposed to talk about the school lunch program this morning, but the vice-principal went off on a tangent about summer camps, and we didn’t reach any decisions.

Example 2: The railroad track is tangential to the curve of the river at the Cross Creek bridge.

Here are some other English words that started out as mathematical terms, but came to have different meanings over the centuries:

average
Math: The result of dividing the sum of a set of values by their number.
English: What is most common or usually expected.
Idiomatic: Ordinary; nothing special.

square
Math: The shape formed by four straight lines of equal length meeting at right angles.
English: An open space in the middle of a town used for public functions.
Idiomatic: To repay a debt or obligation.

circular
Math: In the shape of a circle.
English: Roundabout, avoiding the main issue, coming to no conclusion.
Idiomatic: A flyer or pamphlet (something that is “circulated” to many people).