2

ABSTRACT leaves a small vertical gap as follows.

\documentclass{article}
\begin{document}
\begin{abstract}
There is a vertical gap in between the \textbf{Abstract} right above and this sentence. Can I get the size of this gap---is it \texttt{\textbackslash smallskip}, \texttt{\textbackslash medskip} or \texttt{\textbackslash bigskip}?
\end{abstract}
\end{document}

Can I measure its exact height?

Junyong Kim
  • 533
  • 4
  • 13

1 Answers1

1

Two ways, you can add \showoutput 

\documentclass{article}
\begin{document}
\showoutput
\showboxdepth=4
\begin{abstract}
There is a vertical gap in between the \textbf{Abstract} right above and this sentence.
Can I get the size of this gap---is it \texttt{\textbackslash smallskip},
\texttt{\textbackslash medskip} or \texttt{\textbackslash bigskip}?
\end{abstract}
\end{document}

which shows

....\penalty 0
....\OT1/cmr/bx/n/9 A
....\OT1/cmr/bx/n/9 b
....\OT1/cmr/bx/n/9 s
....\OT1/cmr/bx/n/9 t
....\OT1/cmr/bx/n/9 r
....\OT1/cmr/bx/n/9 a
....\OT1/cmr/bx/n/9 c
....\OT1/cmr/bx/n/9 t
....\penalty 10000
....\glue(\parfillskip) 0.0
....\glue(\rightskip) 0.0 plus 1.0fil
...\glue -5.32494
...\glue 0.0
...\glue 0.0
...\glue 0.0
...\penalty -51
...\glue 10.0 plus 3.0 minus 5.0
...\glue -10.0 plus -3.0 minus -5.0
...\penalty -51
...\glue 10.0 plus 3.0 minus 5.0
...\glue(\parskip) 0.0 plus 1.0
...\glue(\baselineskip) 4.75
...\hbox(6.25+1.75)x294.99994, glue set - 0.0665, shifted 25.00003
....\hbox(0.0+0.0)x13.87491 []
....\penalty 0
....\OT1/cmr/m/n/9 T

so the additional space other than baselineskip between Abstract and There... is

...\glue -5.32494
...\glue 10.0 plus 3.0 minus 5.0
...\glue(\parskip) 0.0 plus 1.0

Alternatively you can look at the source in article.cls

  \newenvironment{abstract}{%
      \if@twocolumn
        \section*{\abstractname}%
      \else
        \small
        \begin{center}%
          {\bfseries \abstractname\vspace{-.5em}\vspace{\z@}}%
        \end{center}%
        \quotation
      \fi}
      {\if@twocolumn\else\endquotation\fi}

so you get the space from the center and quotation lists cancelled out by .5em, note that \end{center} and \quotation lists don't add a double list space as list use \addvspace so latex only adds the maximum of the space after center and the space before quotation.

This construct is kept for historical compatibility, it isn't exactly a model of how to specify document spacing in a coherent way....

David Carlisle
  • 757,742
  • The thing I find peculiar about this is the use of em as the unit for vertical spacing. – barbara beeton Mar 28 '19 at 02:02
  • @barbarabeeton one of the more peculiar aspects, also that it's a fixed (font dependent size) as a negative length counteracting the class-specified display spacing around lists, so if the class were to set the center up with a smaller vertical offset, the abstract could overprint the title having the negative space at all seems "interesting" the fact that it's in em is just icing on the cake... – David Carlisle Mar 28 '19 at 11:52