sand dollar. n. 1. Any of various thin circular echinoderms of the order Clypeasteroida, especially Echinarachnius parma, of coastal northern Atlantic and Pacific waters, having a covering of short movable spines.
One reason why linear algebra is very useful is that linear transforms of normal variables are normal. If x ~ N(a, A), then Bx+b ~ N(Ba+b, BABT). In a way, when everything is linear and normal, everything is nice and analytically tractable.
The takeaway message is. Linear algebra is the study of vectors and linear transformations. In broad terms, vectors are things you can add and linear functions are very. special functions of vectors that respect vector addition. To understand this. a little better, lets try some examples.