As a non-native English speaker, this question about style comes back to me every time I'm writing a formal text.
Given a certain mathematical element, such as a matrix detoned by M. Which is the more correct way to refer to it:
"Note that matrix M is symmetric" or "Note that the matrix M is symmetric" ?
For clarity and correctness, most English speakers would prefer "Note that the matrix $M$ is symmetric" or "Note the matrix $M$ is symmetric" to "Note matrix $M$ is symmetric". This assumes you haven't introduced $M$ yet; if you have, "Note $M$ is symmetric" is fine.