What is the opposite of a cross term?

Question

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?

I'm not aware of standard terminology, but I'd call them "pure terms". — mdp, Mar 28 '12 at 13:15

score 13 · Accepted Answer · answered Mar 28 '12 at 13:22

13

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.

answered Mar 28 '12 at 13:22

joriki

238,052

1

+1, Came here to give this answer. I think I have seen diagonal used most often. – Eric Naslund Mar 28 '12 at 13:29

bgins · Answer 2 · 2012-03-28T13:44:01.350

3

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).

edited Mar 28 '12 at 13:44

answered Mar 28 '12 at 13:36

bgins

7,990

score 2 · Answer 3 · answered Aug 20 '12 at 05:09

2

The univariate terms is unambiguous. I like 'pure' but am not sure how correct this is.

answered Aug 20 '12 at 05:09

Dan

21

score 1 · Answer 4 · answered Mar 28 '12 at 13:18

1

The squares or more general, the $n$th power.

answered Mar 28 '12 at 13:18

draks ...

18,449

score 1 · Answer 5 · answered Mar 28 '12 at 13:22

1

The aligned terms. ............

answered Mar 28 '12 at 13:22

John Bentin

18,454

score 1 · Answer 6 · answered Jan 16 '13 at 18:01

1

The square term or quadrature term is the best.

answered Jan 16 '13 at 18:01

user58507

11

score 0 · Answer 7 · answered Mar 16 '23 at 12:32

0

Cord/chord is the term

Aligned would be the close next term as @John Bentin said. But lines or straight both can apply to cross.

answered Mar 16 '23 at 12:32

L92MD14

11

I am curious why cord (or chord) is a good word choice here. I looked at these definitions, but did not make any useful connection: https://www.dictionary.com/browse/chord – 311411 Mar 16 '23 at 12:52
Cord is close to align as in Verb 2 of 2 in the link here, which where I would start then move onto noun form: https://www.merriam-webster.com/thesaurus/chord – L92MD14 Mar 17 '23 at 01:40
“He was being cordial” vs “He was being cross” – L92MD14 Mar 28 '23 at 12:50

What is the opposite of a cross term?

7 Answers7