Problem with \underline{} command! [duplicate]

Question

I wrote the following commands:

The following {\bf {\underline{Approximations}}} and {\bf\underline{Definitions}} is applied in further work

The things comes out as:

One is way down than other and looks weird. What is the possible solution so that the distance remains same in all text?

Answer 1

Package ulem addresses this problem. It also works for plain TeX (\bf):

\input ulem.sty

The following {\bf\uline{Approximations}} and
{\bf\uline{Definitions}} is applied in further work.

\bye

If you are using LaTeX, then know, that \bf is deprecated since decades.

\documentclass{article}
\usepackage{ulem}
\begin{document}
The following \textbf{\uline{Approximations}} and
\textbf{\uline{Definitions}} is applied in further work.
\end{document}

Package soul also allows hyphenation:

\documentclass{article}
\usepackage[a6paper]{geometry}
\usepackage{soul}
\begin{document}
The following \textbf{\ul{Approximations}} and
\textbf{\ul{Definitions}} is applied in further work.
\end{document}

Typography: Underlining comes from the time of mechanical typewriters. Font switches were tricky at best. But LaTeX allows for different font shapes, and bold is more than enough. The usual emphasis command uses italics. Also several ways for emphasis (bold + underline, bold + italics, ...) should not be used.

\documentclass{article}
\begin{document}
The following \textbf{Approximations} and
\textbf{Definitions} is applied in further work.

The following \emph{Approximations} and
\emph{Definitions} is applied in further work.
\end{document}