# Definition talk:Matrix

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## Notation Abuse?

Is it worth pointing out on the page that, e.g.,

- $\mathbf M = \begin{bmatrix} \mathbf A & \mathbf B \\ \mathbf C & \mathbf D \end{bmatrix}$.

is not a matrix with matrices as entries, rather, we're using the matrix variables to mean "the stuff *in* the matrix"? I've been using this notation both in my personal lecture notes and on proofwiki without thinking it an important distinction. --GFauxPas (talk) 14:10, 27 January 2013 (UTC)

- If you like, but it's probably not that important as the notation as used here is standard and understood to mean what we have described. Incidentally, is there any difference? Can it be argued that the brackets around the matrix are conceptual only and therefore do not have the same force of meaning as the brackets around a set? That is, $\left\{{A, B, C, D}\right\}$ where $A, B, C, D$ are sets is not the same as $\cup \left\{{A, B, C, D}\right\}$ which would be the conceptual analogue.

- Fancy doing some research? --prime mover (talk) 14:59, 27 January 2013 (UTC)

- This reminds me of this and this. I have come to clump such things under the heading of 'Notational Baggage'. It is just my opinion however and I do see the value of pointing out such things. Such issues would be especially important to the NLP specialists working behind the scenes at Wolfram|Alpha --Jshflynn (talk) 20:13, 27 January 2013 (UTC)