# “]” not working [duplicate]

I tried to compile something like the following but it is not compiling:

$$\begin{array}{ccc} [u,v]=0&,&\text{if bla}\\ [u,v]=0&,&1 \end{array}$$


I also tried

\begin{eqnarray}
[u,v]=0&,&\text{if bla}\\
[u,v]=0&,&1
\end{eqnarray}


I'm using pdflatex (Windows prompt), Version 3.1415926-1.40.10 (MiKTeX 2.8), and the compiler shows

! Missing number, treated as zero.
u
1.45                    [u,v]
=0 &,&1
?


Sincerely, this makes no sense for me and if I delete the "]" in the second line, or if I don't use the second line in the eqnarray (or array), it compiles normally.

## marked as duplicate by Werner, Torbjørn T., Svend Tveskæg, David Carlisle, egregNov 12 '13 at 23:13

• use {}[ as otherwise the [ is taken as the optional argument to \\  also don't use  in latex (this is a duplicate, I'll add a link in a bit) – David Carlisle Nov 12 '13 at 22:56