When consumption or production of a product has a harmful side effect that is borne by people not directly involved in the market exchange for that product, the side effect is called a(n):

An external cost.

Explanation:

An external cost is the cost borne upon by a third party, maybe an individual, firm or community as a result of a market exchange for a product which they are not directly involved in. And this can occur in both production and consumption.

i think it because equal matrices have equal dimensions, only square matrices can be symmetric. for all indices and . every square diagonal matrix is symmetric, since all off-diagonal elements are zero. in linear algebra, a real symmetric matrix represents a self-adjoint operator over a real inner product space.