Labelling commands for quick use

Question

I have a certain command in LaTeX that I have used a lot in my current work:

{\bf y} # this creates a bold letter y

I want to create a shortcut e.g.

\by

that will automatically create a bold letter y. I have similar expressions I would like to simplify as my equations are getting pretty long. Any advice would be appreciated.

Answer 1

This is done with \newcommand, i.e.:

\newcommand{\by}{\textbf{y}} 

There is more functionality in it than just substituting, i.e., you can have arguments there. Please find more info and some examples here.

Answer 2

\newcommand is the command you look for (see sashkello answer)

There are some things you should look for:

\documentclass{scrartcl} 
\newcommand{\by}{\textbf{y}} 

\begin{document}
Now we write a \by and a x.    
\end{document}

The y is direct connected to the and.

You may add a space in \newcommand to add a space before the and:

\documentclass{scrartcl} 

\newcommand{\by}{\textbf{y} } %<- space before the closing }

\begin{document}
Now we write a \by and a x.

Now we write a \by. The next sentence.

\end{document}

The next problem: There is an additional space when you start a new sentence.

For this problem you may use \xspace:

\documentclass{scrartcl} 
\usepackage{xspace} 

\newcommand{\by}{\textbf{y}\xspace}

\begin{document}
Now we write a \by and a x.

Now we write a \by. The next sentence.

\end{document}

The result: