The unique maximal ideal of a (commutative) local ring contains all of the zero divisors of such ring, and all elements of the ring outside of it are units. Then in a local ring, the sum of any two zero divisors is also a zero divisor. Contrapositively, if two ring elements add up to a unit then one of them must be a unit as well. A simple example of a local ring is ℤ₈.

‘A rough fellow, rather, Mrs. Dean. Is not that his character?‘ ‘Rough as a saw-edge, and hard as whinstone! The less you meddle with him the better.’

A contaminant came up with the brine . . . rock oil . . . petroleum . . . Texas tea.

Have you tried the new tacos from that restaurant? They're pretty bomb!