# How to get spacing in math mode without just repeating fixed spaces (tilde ~)?

I'm looking for a way to move text in my equation, instead of just shoving multiple ~~~~ until it's in the right position. I'm quite new to LaTeX, what exactly would be the command?

I'm also looking for a way such that this command won't move the position of anything anything before it, but of course moves forward everything in front.

Right now I have:

\begin{equation*}
\begin{aligned}
\frac{\partial \Psi}{\partial x} &= 0     \mbox{ for } 0 \leq y \leq b \\
\frac{\partial \Psi}{\partial y} &= 0     \mbox{ for } 0 \leq x \leq a \\
\end{aligned}
\end{equation*}


I'm trying to increase the distance between the end of the fraction and the start of the text "for".

• Welcome to TeX.SE! Have you tried \quad and/or \qquad to create the desired gap? – Mico Apr 20 '14 at 21:20
• using \text{...} instead of \mbox{...} is recommended. – barbara beeton Apr 21 '14 at 5:17

Instead of using nested equation* and aligned environments, you could use a single align* environment. Two additional suggesions: (i) for the separation between the equation and condition parts, you could employ \qquad ("double \quad"); (ii) for a bit more vertical separation between the two rows, you could [1ex] immediately after the first \\ line break instruction.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
\frac{\partial \Psi}{\partial x} &= 0 \qquad\text{for $0 \leq y \leq b$} \\[1ex]
\frac{\partial \Psi}{\partial y} &= 0 \qquad\text{for $0 \leq x \leq a$} \\
\end{align*}
\end{document}

• better to use && before the \text just in case what is on the right-hand side of the = signs isn't always the same width. – barbara beeton Apr 21 '14 at 6:05
• @barbarabeeton - Good point. I guess I was working with what the OP stated he/she wants to get typeset... – Mico Apr 21 '14 at 6:14

If you don't want the equations numbered (since you are using aligned), just adding a && after the = 0 on each row will insert a \quad = 1em horizontal gap between the equation and what follows AND left-align the following content (a single & would also add the 1em gap, but right-align what follows). The aligned type environments are aligned rlrlrl..., with a 1em gap after each left-aligned field.

An alternative method is also shown here, with a TABstack, in which the horizontal and vertical gaps between the equation parts may be independently specified.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tabstackengine}
\stackMath
\begin{document}
Original
\begin{equation*}
\begin{aligned}
\frac{\partial \Psi}{\partial x} &= 0     \mbox{ for } 0 \leq y \leq b \\
\frac{\partial \Psi}{\partial y} &= 0     \mbox{ for } 0 \leq x \leq a \\
\end{aligned}
\end{equation*}
Extra alignment tab in aligned environment
\begin{equation*}
\begin{aligned}
\frac{\partial \Psi}{\partial x} &= 0&&     \mbox{ for } 0 \leq y \leq b \\
\frac{\partial \Psi}{\partial y} &= 0&&     \mbox{ for } 0 \leq x \leq a \\
\end{aligned}
\end{equation*}
a tabstack with vertical and horizontal gap size set
\setstackaligngap{3em}
\setstackgap{S}{8pt}
\begin{equation*}
\alignShortstack{
\dfrac{\partial \Psi}{\partial x} &= 0 &&\mbox{ for } 0 \leq y \leq b \\
\dfrac{\partial \Psi}{\partial y} &= 0 &&\mbox{ for } 0 \leq x \leq a \\
}
\end{equation*}
\end{document}


Other alternatives for horizontal space in equations, when tab alignment is not the appropriate method, can be accomplished either with \hspace{length}, with \kern length, or with \mkern mu-length. Additionally, as was pointed out in the comments, \quad and \qquad also insert "typical" (recommended?) math separations. With \hspace, inserted glue can be a factor (though I don't know if that is relevant in math mode), whereas no glue will be inserted about kerns.

The alignat environment can do what you want. Here are two suggestions — the second one requires using the mathtools package, which loads amsmath anyway:

\documentclass{article}

\usepackage{mathtools}

\begin{document}

\noindent A first solution:
\begin{alignat}{2}
\frac{\partial \Psi}{\partial x} &= 0 & \hspace{4em} & \mbox{ for } 0 \leq y \leq b \\
\frac{\partial \Psi}{\partial y} &= 0  &  &  \mbox{ for } 0 \leq x \leq a + 1
\end{alignat}
Or even,  keeping the first column centred:
\begin{alignat}{2}
\frac{\partial \Psi}{\partial x} &= 0 & \hspace{4em} & \mathrlap{\mbox{ for } 0 \leq y \leq b} \\
\frac{\partial \Psi}{\partial y} &= 0  &  & \mathrlap{\mbox{ for } 0 \leq x \leq a  + 1}
\end{alignat}
\end{document}