# Non left-aligned equations

My equation is not left-aligned; see the attached image. I'd like it to be left-aligned.

\begin{equation} P(w_{i} | h) =   \left\{
\begin{aligned}
\frac{n(h, w_{i})}{n(h)}    Si n(h, w_{i}) > k\\
d_{r} \frac{n(h, w_{i})}{n(h)}\\
\alpha(h) P(w_{i} | h^{-1}\\
\end{aligned}
\right.
\end{equation} • The first column in an alignment is right aligned. You might want to have a look at the cases env, faster to use as the { is build in Oct 21 '15 at 19:38

While you can use an aligned environment, your use is better-suited for the cases environment: \documentclass{article}

\usepackage{amsmath}
\DeclareMathOperator{\Sin}{Sin}

\begin{document}

\begin{equation}
P(w_i \mid h) = \begin{cases}
\dfrac{n(h, w_i)}{n(h)} \Sin(h, w_i) > k \\
d_r \dfrac{n(h, w_{i})}{n(h)} \\
\alpha(h) P(w_i \mid h^{-1})
\end{cases}
\end{equation}

\end{document}


If you want to use aligned, you have to add an ampersand &:

\begin{equation} P(w_{i} | h) = \left{
\begin{aligned}
& \frac{n(h, w_{i})}{n(h)}    Si n(h, w_{i}) > k\\
& d_{r} \frac{n(h, w_{i})}{n(h)}\\
& \alpha(h) P(w_{i} | h^{-1}\\
\end{aligned}
\right.
\end{equation}


The formula in each row of the aligned environment can be structured by putting & at the right places. The idea is that corresponding &s of different rows will be aligned on top of each other. In order to align arbitrary formulas at specific points, the parts before the first & is right aligned, the part after the second & is left aligned, and then it alternates.