Over- and Underlining (LaTeX2e unofficial reference manual (November 2018))

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### 16.5 Over- and Underlining

LaTeX provides commands for making overlines or underlines, or putting braces over or under some material.

`\underline{text}`

  Underline text. Works inside math mode, and outside. The line is always completely below the text, taking account of descenders, so in `\(\underline{y}\)` the line is lower than in `\(\underline{x}\)`. This command is fragile (see \protect).

  Note that the package `ulem` does text mode underlining and allows line breaking as well as a number of other features. See the documentation on CTAN. See also \hrulefill & \dotfill for producing a line, for such things as a signature.

`\overline{text}`

  Put a horizontal line over text. Works inside math mode, and outside. For example, `\overline{x+y}`. Note that this differs from the command `\bar` (see Math accents).

`\underbrace{math}`

  Put a brace under math. For example, this `(1-\underbrace{1/2)+(1/2}-1/3)` emphasizes the telescoping part. Attach text to the brace by using subscript, `_`, or superscript, `^`, as here.

      \begin{displaymath}
        1+1/2+\underbrace{1/3+1/4}_{>1/2}+
             \underbrace{1/5+1/6+1/7+1/8}_{>1/2}+\cdots
      \end{displaymath}

  The superscript appears on top of the expression, and so can look unconnected to the underbrace.

`\overbrace{math}`

  Put a brace over math, as with `\overbrace{x+x+\cdots+x}^{\mbox{\(k\) times}}`. See also `\underbrace`.

The package `mathtools` adds an over- and underbrace, as well as some improvements on the braces. See the documentation on CTAN.

Unofficial LaTeX2e reference manual