12

Perhaps it was just being misused, but the questions crossed my mind before and last night it came up again again.

While talking with someone about job opportunities in NYC, a friend started to talk about cost of living. As we continued to discuss various pros and cons, the friend said to me

Let's get back on the job discussion, cost of living is tangentially related but not important right now.

In this instance, the friend was saying that what we were talking currently (cost of living) has a close relationship with what we started on (working in NYC).

Later in the conversation, our conversation turned towards the amount of time it takes to move from Colorado to NYC. As we talked about the various routes and vehicles for movement, the friend said:

We've gone way off topic — talk about getting lost on a tangent.

In this instance, the tangent is barely related to the original subject.

Is there a misuse of the word tangent here, has tangent just become a word that relates to anything off-topic that has at least the slightest relation to the original topic, or is there something else that I am missing?

Tangentially related question

  • 35
    @MaxWilliams I was sure tangentially related meant remotely related. – Aeon Akechi Jul 28 '16 at 13:45
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    The terms tangentially related ... not important are a clue that the tangential relationship was not a "close relationship" with "what [you] started on". In both cases, the tangent / tangential relationship bears only a weak relationship (if any) with the topic at hand. – Lawrence Jul 28 '16 at 14:24
  • 7
    Lawrence is right. If there's redundancy, it's in having the word "related" rather than "tangential." If two things are tangential, they have 1 common point, and so must be related. Two things may, however, be much more deeply and intimately related than that. Of course, in speech, "tangential" on its own is uncommon, so I think that "tangentially related" isn't phrasing you can fault someone for (even if it is technically redundant). You cannot say, however, that 'tangentially related' "just" means 'related.' – Non-Contradiction Jul 28 '16 at 14:29
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    I suppose that one use of tangential could be replaced with peripheral to make the meaning clearer - while langential (literally: "touching") does imply "close", it only means "close to the boundary", not "close to the core" – Hagen von Eitzen Jul 28 '16 at 19:37
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    I think your interpretation is just wrong: "cost of living is tangentially related but not important right now" is meant to imply "cost of living is not very closely related to working in NYC". Possibly you just disagree with that assessment? – Jonathan Cast Jul 29 '16 at 18:59
72

"Tangent" is a math term that's been picked up by the language at large. It describes a straight line that contacts a circle or curve at exactly one point. It doesn't intersect; it makes contact and then keeps going on the same side of it. On the one hand, two subjects that have one point of contact are "tangentially" related. On the other, once you start going on a tangent, you will keep going and going further away from your original topic and (presumably) never come back to it.

(When the tangent contacts a curve that isn't a circle, it's possible that the tangent may intersect the curve somewhere else, as, for example, in the cited Wikipedia article.)

  • 3
    I was writing something along these lines... but you beat me to it. :) +1. – Ghotir Jul 28 '16 at 13:35
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    I said that it's a "straight line that contacts a circle or a curve at exactly one point. (It doesn't intersect; it makes contact and then keeps going on the same side of it.)" You say that it's "the straight line that touches the curve at p, and has identical slope as the curve at that point." What's substantially different about those? Yours is more technically worded; that's all. If it's about intersections, obviously a tangent to a curve can intersect it - as the prominent picture on the Wikipedia page I posted depicts - but because of its use in language, I saw no reason to belabor it. – Non-Contradiction Jul 28 '16 at 19:57
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    @Non-Contradiction A tangent at one point can intersect the curve at other points. If the curve is convex (like a circle), this can't happen, and the sense of "tangent" that's filtered into common English is this more restricted sense (which is why I upvoted your answer despite it being technically incorrect in the mathematical sense.) – Monty Harder Jul 28 '16 at 22:18
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    Martin's first comment is right. The definition given by Wikipedia (as cited in my original answer) is "In geometry, the tangent line (or simply tangent) to a plane curve at a given point is the straight line that "just touches" the curve at that point." It's not unhelpfully technical, gets the idea across, and, yes, is accurate. My original def. is basically a re-wording with the idea of plane-ness sidelined. The inclusion of ellipses is both distracting to the pedestrian and insufficient for the mathematician. If someone needs more, I've linked to Wikipedia right there. – Non-Contradiction Jul 29 '16 at 14:25
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    I think that although Martin's second comment is technically correct, my post is also acceptable and more useful. "Tangent" describes straight lines commonly enough for that to be the explicit genus in basic definitions - and, moreover, it is what almost everyone whose math education is confined to high school geometry and calc imagines. For the colloquial use, people's idea when they use "tangent" in speech is a straight line - it's not one circle confined by another or adjacent, it's a single point of contact followed by an infinity of increasingly distant points. – Non-Contradiction Jul 29 '16 at 17:22
44

Tangent does not have conflicting meanings.

In the first example you were talking about jobs in NYC, started talking about something that was tangentially related (cost of living), realised that you were going off on that tangent, and took it back to talking about the job.

In the second example you were talking about jobs in NYC (I think), started talking about something that was tangentially related (moving to NYC), and realised you'd spent a long time on that tangent.

The only difference between the two examples is how far you went down the tangent, not what "tangent" meant.


For a discussion on what "tangent" means, see the answer by Non-Contradiction. But I felt it didn't cover the key point, i.e. that the assertion in the question title was incorrect.

  • I agree that there is no conflicting meanings. Instead the purported topic was misrepresented. Rather than being a discussion about jobs in New York, it was about a potential opportunity to relocate to New York for a new job. So the first example of the cost of living is really an integral part of that discussion. Would you move from an area where 50% of your check goes to cost of living to an area that requires 99% of what you earn, even if you are earning double in terms of actual dollars? The second example is related to the topic because moving is a significant part of the decision. – huckleseed Jul 28 '16 at 21:03
6

The word tangentially is derived from Latin tangens, which means touching.

In maths, a tangent is a straight line that touches (not intersecting with) a circle or ellipse.

The discussion about the costs of living touches the discussion about job in the sense that they have something in common (in NYC, you earn a lot more money, but life is more expensive). So the Latin word tangens fits here, too, and hence the same English derivative word as in maths is used.

1

If you tie a rope to a weight, sling the rope around over your head in a wide circle, then suddenly let go of the rope, "tangent" mathematically describes the path the weight will take as it flies off.

With this image in your head, it's easy to understand the metaphorical use of the word "tangent". The weight goes off in a somewhat unpredictable direction (unless you have the skills of a David killing the Biblical Goliath), and, even though it moves (theoretically, at least) in a straight line, it's not a line that coincides with the center of your body, but rather one that intersects the (somewhat random) position of the weight at the point of release.

So, cost of living is tangentially related to the discussion, but doesn't seem to relate to its center. And if you don't pay attention to where/how you release the rope, it and the weight may go off in the weeds and be lost on a tangent.

  • Ummmm.... no, it doesn't. "Tangent" only describes the immediate position of the weight relative to the constrained circular path at the moment of release. – Carl Witthoft Jul 29 '16 at 14:31
  • @CarlWitthoft - Granted, one must assume "ideal" conditions, with no friction, gravity, or other force affecting the weight, but, if you do that, Newton tells us the weight will follow a tangential path. – Hot Licks Jul 29 '16 at 15:31

protected by tchrist Jul 31 '16 at 13:50

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