I'm not a mathematician, and the last time I studied maths was a good eight years ago. I'm going through a book called 'An Introduction to Recommender Systems', and in section 2.4.1 it refers to table 2.4 (see image below)
It says "Because the 4 x 4-matrix M in Table 2.4 is quadratic, U, E, and V are also quadratic 4 x 4 matrices"
I'm not quite sure how a conclusion was drawn that the matrix is 'quadratic'. I can't find anything describing what a 'quadratic matrix' is via Google. I would assume that it is a way to describe a matrix of numbers that have been squared, but that's not the case in table 2.4 above as these numbers were introduced as single values at the start of this chapter, and have not been squared since then.
Would anybody mind telling me if this is an obscure mathematics, or academic term? And/or what it means?
Here's the full page, if anybody is interested in viewing it in context.
Reference: (Felfernig, A. et al., Recommender Systems: An Introduction, New York, Cambridge University Press, 2011)