I am translating a material on visual sensors and having a hard time figuring out what to call this.

The situation is that when the sensor senses a circle mark, sometimes it does not detect a fine circle. Instead, the circle becomes a little wavy, having some parts of outline sticking out of the real line, and some parts going inside.

I need to express the length of the difference between the real line and the off-points of the detected line. I came up with the following two expressions. Does either of them indicate what I am trying to say?

Positive/negative difference” OR “Positive/negative deviation length”.

  • I'd go for: Inner/Outer deviations.
    – Joe Dark
    Dec 4, 2014 at 0:44
  • 1
    Terms like radial error or diametral error may be relevant, and also runout Dec 4, 2014 at 1:46
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    If you are talking only about circles (or circular object, such as cylinders, cones, and spheres), then the noun is out-of-round. The adjective would be out-of-roundness.
    – Drew
    Dec 4, 2014 at 3:33
  • This question is dated, but hoping somebody sees this addition: can they also be called "positive/negative offset"?
    – Jun Kyoto
    Jan 13, 2015 at 6:18

1 Answer 1


I think simply "deviation" is fine. Deviation is already defined as "a measure of difference between the observed value of a variable and some other value".

So I'm pretty certain you don't even need the "length"-part. The term "deviation in length" is only used when referring to an actual difference in length.

I'd go for "The deviation between the two lines in [unit] is X".

  • 1
    Thank you J, just to confirm, does "positive/negative deviation" seem also appropriate? I need to explain this "concept" in the material, so adding minus (-) to the value will not work.
    – Jun Kyoto
    Dec 4, 2014 at 1:00
  • Yes. <p>The sign of the deviation (positive or negative), reports the direction of that difference (the deviation is positive when the observed value exceeds the reference value). The magnitude of the value indicates the size of the difference.</p> from Wikipedia. I wasn't 100% sure either so I checked it out.
    – J_LV
    Dec 4, 2014 at 1:03
  • Just read your edit. Yes, it's appropriate. The terms negative deviation and positive deviation are often used to explain that concept (Check out the article on Raoult's Law for instance).
    – J_LV
    Dec 4, 2014 at 1:07
  • Thank you, I have already seen the Wikipedia page, but thank you for confirming. I will have to be more careful reader.
    – Jun Kyoto
    Dec 4, 2014 at 1:08

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