As far as I know, LaTeX uses four sizes for delimiters: \big, \Big, \bigg and \Bigg (in addition to the normal text size). I through that automatic sizing done by \left ... \right chose on of these. But things seem different with unicode-math; I get with

\left\lvert \frac{\Delta y}{y} \right\lvert

a size which is between \Big and \bigg.

So, my questions:

  1. How works automatic sizing of delimiters with unicode-math?
  2. Can I specify a delimiter size for \frac{\Delta x_1}{x_1} identical to the size got with \left\lvert \frac{\Delta y}{y} \right\lvert (something between \Big and \bigg), without having to \smash the subscript?





  \text{letft...right}                        &  &
  \text{big}                                  &  &
  \text{Big}                                  &  &
  \text{bigg}                                 &  &
  \text{Bigg}                                 &  &
  \left\lvert \frac{\Delta y}{y} \right\lvert &  &
  \bigl\lvert \frac{\Delta y}{y} \bigr\lvert &  &
  \Bigl\lvert \frac{\Delta y}{y} \Bigr\lvert &  &
  \biggl\lvert \frac{\Delta y}{y} \biggr\lvert &  &
  \Biggl\lvert \frac{\Delta y}{y} \Biggr\lvert &  &
  \left\lvert \frac{\Delta x_1}{x_1} \right\lvert &  &
  \bigl\lvert \frac{\Delta x_1}{x_1} \bigr\lvert &  &
  \Bigl\lvert \frac{\Delta x_1}{x_1} \Bigr\lvert &  &
  \biggl\lvert \frac{\Delta x_1}{x_1} \biggr\lvert &  &
  \Biggl\lvert \frac{\Delta x_1}{x_1} \Biggr\lvert &  &



  • 2
    That assumption is wrong. Left/right does whatever it does whereas as the big sizes are fixed. Otherwise one could never get sizes larger than Bigg. Has nothing to to with unicode-math, you should get the same answer without it.
    – daleif
    Commented Jun 24 at 9:36
  • @daleif Without unicode-math I get the same size as with \bigg.
    – jlab
    Commented Jun 24 at 9:41
  • 1
    @jlab, completely by chance ...
    – Zarko
    Commented Jun 24 at 10:20

1 Answer 1


The classical TeX and classical Computer modern fonts implement delimiters with given step between sizes. All small sizes are accessible via plain TeX macros \big, \Big, \bigg, \Bigg. Larges sizes are implemented using a small piece of the delimiter which is repeated one above other to construct the whole delimiter. The height of this piece is the given size of the step.

This follows typographical rules that delimiter cannot have arbitrary size but sizes distinguished directly in their size by a given step.

Now, we have not only 7-bit Computer Modern fonts and not only classical TeX math, but we have a plenty Unicode math fonts. They implement the step between sizes of delimiters too (in order to follow the typographical rule), but this step cannot be equal with the step from old Computer Modern fonts. The step realized by \left, \right primitives in Unicode math fonts could be softer. But the macros \big, \Big, \bigg, \Bigg (originally in plain TeX) implement direct dimensions for each size and they don't have to respect the size step from used Unicode math font. This is the case you shown.


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