What is the opposite of a cross term?
When we multiply out $(x + y)(x + y)$, we refer to the two $xy$ terms as "cross terms". Is there a corresponding term for the $x^2$ and $y^2$ terms?
$\endgroup$ 36 Answers
$\begingroup$Depending on the context, "diagonal terms" might work:
$$(x+y)(x+y)=\pmatrix{x&y}\pmatrix{1&1\\1&1}\pmatrix{x\\y}\;;$$
the cross-terms are the off-diagonal terms in this quadratic form and the other ones are the diagonal terms.
$\endgroup$ 1 $\begingroup$Direct or straight might be what you are looking for, as opposed to cross, crossed or mixed (since each resultant term has either one variable to a power or two different variables, a "mixture").
I was also taught that you can multiply $(a+b)(c+d)$ using the acronym FOIL for First, Inside, Outside, Last (which is mixing sequential and spatial metaphors).
$\endgroup$ $\begingroup$The squares or more general, the $n$th power.
$\endgroup$ $\begingroup$The aligned terms. ............
$\endgroup$ $\begingroup$The univariate terms is unambiguous. I like 'pure' but am not sure how correct this is.
$\endgroup$ $\begingroup$The square term or quadrature term is the best.
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