= Typesetting glue order
A \b[typesetting glue order] assigns a priority to stretch or shrink in <TeX>. The orders are normal finite flexibility, `fil`, `fill` and `filll`, in increasing priority. With nonnegative coefficients, the highest present order absorbs the adjustment; lower-order flexibility is left unused.<TeX source code by Donald E. Knuth>[glue_spec fields and hpack/vpack: highest nonzero order for glue setting]{ref}
For example, suppose a line has natural width 22 and must reach width 34. Two zero-width glue items have stretch coefficients `1fil` and `2fil`. Their added widths are
$$
\boxed{\Delta_1=12\frac{1}{3}=4,\qquad \Delta_2=12\frac{2}{3}=8.}
$$
A finite-order glue item in the same line keeps its nominal width during this adjustment. The symbols define priorities for distributing a finite width difference. Within the selected order, the coefficients still determine proportional sharing.
The simple finite model in <typesetting glue> uses only the normal order. Higher orders make it possible to place flexible space at selected locations, such as before or after a line's content, without requiring the ordinary <word spacing> to absorb that particular adjustment.
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