OK, I've seen related questions which indicate that you only bold the main symbol and not subscripts, and a few other almost related questions. But what about when you are using a bold math symbol dotted?

That is, I have a letter which represents a vector. We've been writing vectors as bold letters, i.e \mathbf{u}.

We represent the first time derivative of this symbol by putting a dot on it. Should I bold the dot or not? That is choice:

  1. \mathbf{\dot{u}}, or
  2. \dot{\mathbf{u}}

Edit: All things equal, I prefer the way choice 2 looks.

  • 1
    In a general setting, applying some formatting to a symbol (letter, or otherwise) changes its meaning. In a similar way that U is different from \mathcal{U}, say. So, I would keep the operator symbol (\dot in this case) the same and therefore not bold.
    – Werner
    Apr 29, 2013 at 0:13
  • 1
    I'd keep option 2. You are differentiating the vector, and thus there is no reason why the dot should be inside the "bolding" command. Apr 29, 2013 at 0:18
  • Ah the author forgot \dot inside the \mathbf... would be my reaction to that.
    – percusse
    Apr 29, 2013 at 0:18
  • @percusse huh? reaction to what?
    – Jeff
    Apr 29, 2013 at 0:24
  • Reading a bold dot.
    – percusse
    Apr 29, 2013 at 0:27

1 Answer 1


No, you should not print the dot bold. It \dot means a derivative, why should one assume that it's bold version have the same meaning?

  • 1
    I think you misinterpret what the OP was asking. The bold part of the symbol means it's a vector. What he is asking is whether the dot (meaning the first derivative) should also be bold as well. Apr 29, 2013 at 0:15
  • @MarioS.E. It is difficult to give a meaning of (skalar) derivative of a vector, indeed. But if \matxbf{f}=(x^2,0,1) one can interprete its vector derivative as the scalar one. Apr 29, 2013 at 0:25
  • @e-birk Thank your for your comment. My answer is earlier than OP's edit. (Corrected, as you had suggested). Apr 29, 2013 at 17:46

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