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In some cases where weird spacing can happen, it is recommended to add (possibly empty) braces, e.g.

  • Using \underbrace and similar (link): 
    \[
    { \underbrace{a}_{b} } + c
\]
  • Aligning relation symbols on the right side with amsmath package: 
    \begin{align*}
        {} & a \\
    \iff{} & b
\end{align*}
    or 
    \begin{align*}
    a ={} & b + c + d \\
       {} & + e + f
\end{align*}
    (Bonus question: Why don't we need to do it if we align on the left side, like &= instead of & {}=?)

Are there any other use cases of braces in math mode one should know of?

Bernard
  • 271,350
Gargantuar
  • 725
  • A brace group {...} constructs a sub_mlist which behaves like a mathord with regards to spacing. Personally I wouldn't use {...} but rather be explicit by using \mathord{...}. – Henri Menke Apr 15 '22 at 14:39
  • An empty brace group {} will result in an empty noad node which also behaves like a mathord. – Henri Menke Apr 15 '22 at 14:40
  • You need no empty group on the right of an alignment point & because the left-aligned columns already start with an empty group. I've described the working of align a bit in this answer of mine. (Actually the answer is about aligned but the main points are the same.) – campa Apr 15 '22 at 17:13
  • The "short" answer would be "read the whole TeXbook"... – user202729 Apr 15 '22 at 17:13

0 Answers0