I've seen that referred to as the antidiagonal. Not sure how common the usage of that is though.

**Thank you.**

Searching for "antidiagonal" gave other terms also used:

subsidiary diagonal

secondary diagonal.

Subsidiary diagonal can be confushed with superdiagonal/subdiagonal when refering to tridiagonal matrices.

The "main diagonal" is the "primary diagonal" and the "antidiagonal is the "secondary diagonal".

I like that.

Again, Thank you.

Example: 2x2 matrix

The diagonal from the upper left to the lower right is identified as "main diagonal".

The trace(*A*) is the sum of the elements along the main diagonal.

The question: Is there a name for the diagonal from the Lower-left to the upper-right?

Or do you have a reference/resource that might have a name for this diagonal?

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