Why are h and k generally used to denote the coordinates of the center of a circle?

After a bit of research, we found that h may represent "horizontal shift" or "horizontal translation", but we're not sure, and we can't figure out what k represents.


  • $\begingroup$ This MetaFilter question is related to this one. Note that someone said it was about alphabetical progression, so from $h$, people went to $i$ and skipped it because imaginary numbers, people went to $j$ and skipped it because imaginary numbers in engineering, and then settled on $k$. $\endgroup$ May 19, 2016 at 20:42
  • $\begingroup$ Ok, that seems possible. Is there any evidence for that? Thanks! $\endgroup$
    – Nisala
    May 19, 2016 at 20:44
  • $\begingroup$ It was just a conjecture someone wrote on MetaFilter, but they did not give any evidence. $\endgroup$ May 19, 2016 at 20:45
  • 2
    $\begingroup$ I find odd that one contests that this is standard notation. In my experience much more common is $(x_0, y_0)$ or $(a,b)$. $\endgroup$
    – Git Gud
    May 19, 2016 at 20:47


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