# Matrix notation differences

So I'm in an elementary matrix and linear algebra class and during lecture my professor uses this notation for a matrix: $$\left(\begin{matrix}a & b\\c&d\end{matrix}\right)$$ but in my textbook it uses $$\left[\begin{matrix}a & b\\c&d\end{matrix}\right]$$ Is there a difference here?

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No, no difference. –  julien Jan 26 '13 at 20:32

$$\left(\begin{matrix}a & b\\c&d\end{matrix}\right)\quad = \quad \left[\begin{matrix}a & b\\c&d\end{matrix}\right]$$

"Is there a difference here?" Not at all.

Just search this site for "matrices" and you'll see both the use of parentheses and brackets, with similar frequency.

Similarly, with vectors, you'll see them written as ordered 'tuples with parentheses and sometimes in brackets:

$(\vec{v_1},...,\vec{v_n}) = [\vec{v_1},...,\vec{v_n}]\quad$ and $\quad (\vec{v_1},...,\vec{v_n})^T = [\vec{v_1},...,\vec{v_n}]^T$

It is probably easier on a chalkboard (or by hand, for that matter) to write matrices with parentheses, whereas in typesetting, one way is as easy as the other.

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I prefer the first shape, always. –  B. S. Jan 26 '13 at 20:21

The body must be at least 30 characters, but the answer needs only three:

No.

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You mean . takes a one character? :D –  B. S. Jan 26 '13 at 20:21
Well, yes: .... –  k.stm Jan 26 '13 at 20:22
@BabakSorouh: en.wikipedia.org/wiki/Character_(computing) –  Rahul Jan 27 '13 at 1:58
There's no difference there. By the way, my understanding is that in Russia, it is common to denote a matrix by $$\begin{vmatrix} a& b\\ c &d \end{vmatrix}$$ and its determinant by $$\begin{Vmatrix} a& b\\ c &d \end{Vmatrix}$$ whereas (at least in the US) we would use the first of these notations for the determinant, and one of the notations you mention in your question for the matrix itself.