“Left-hand Side” and “Right-hand Side”

The command \lhs inserts "left-hand side" or "L.H.S." depending on the context. Similarly, \rhs inserts "right-hand side" or "R.H.S.". When used in text, the macros generate the spelled out text (i.e., "left-hand side"). In math mode, the acronym abbreviation is used.

Definition

\usepackage{xspace}
% Define \lhs for "left-hand side" in text or "L.H.S." in math. 
\newcommand{\lhs}{\relax\ifmmode\mathrm{L.H.S.}\else{}left-hand side\xspace\fi}
% Define \rhs for "right-hand side" in text or "R.H.S." in math. 
\newcommand{\rhs}{\relax\ifmmode\mathrm{R.H.S.}\else{}right-hand side\xspace\fi}

Examples

Code	Output
To simplify the \lhs, we ...	$$\text{To simplify the left-hand side, we ...}$$
To simplify the \rhs, we ...	$$\text{To simplify the right-hand side, we ...}$$
To simplify the $\lhs$, we ...	$$\text{To simplify the L.H.S., we ...}$$
To simplify the $\rhs$, we ...	$$\text{To simplify the R.H.S., we ...}$$