How to solve “Missing delimiter (. inserted) \end{eqnarray*}”? [duplicate]

This question is an exact duplicate of:

How can I solve this problem? I have so many similar to this problem.

marked as duplicate by Henri Menke, Stefan Pinnow, Martin Schröder, Zarko, Torbjørn T.Jun 22 '17 at 7:42

This question was marked as an exact duplicate of an existing question.

You just need to add . after \right even if there is nothing to show in the typeset. This informs TeX engine that the brackets now ended. Check this code for example:

\begin{equation}
P_{e, \thinspace WT} =
\left \{
%
\begin{aligned}
%
& 0  &   & v_{w} \thinspace < \thinspace v_{ci}
\\
& P_{GCR} (v_{w}) \quad   & v_{ci} \thinspace \leq \thinspace &  v_{w} \thinspace \leq v_{r}
\\
& P_{r, \thinspace WT}   & v_{r} \thinspace \leq \thinspace  &  v_{w} \thinspace \leq v_{co}
\\
& 0  &   & v_{w} > \thinspace v_{co}
%
\end{aligned}
%
\right
%
\label{eq:WTPSC}
\end{equation}

Without the dot after \right, you will get a similar error to that shown above. Use the following code (the same as above but with \right.):

\begin{equation}
P_{e, \thinspace WT} =
\left \{
%
\begin{aligned}
%
& 0  &   & v_{w} \thinspace < \thinspace v_{ci}
\\
& P_{GCR} (v_{w}) \quad   & v_{ci} \thinspace \leq \thinspace &  v_{w} \thinspace \leq v_{r}
\\
& P_{r, \thinspace WT}   & v_{r} \thinspace \leq \thinspace  &  v_{w} \thinspace \leq v_{co}
\\
& 0  &   & v_{w} > \thinspace v_{co}
%
\end{aligned}
%
\right.
%
\label{eq:WTPSC}
\end{equation}

You will get: Which means after finishing all of the cases close the set of equations, but not with another curly bracket - simply close it with the "nothing" bracket!