- Morrow County, Oregon (Wikipedia)
Morrow County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 12,186. The county seat is Heppner. The county is named for one of its first settlers, Jackson L. Morrow, who was a member of the state legislature when the county was created. Half of the Umatilla Chemical Depot, which includes the Umatilla Chemical Agent Disposal Facility, and the Naval Weapons Systems Training Facility Boardman are located within the county. Morrow County is part of the Pendleton-Hermiston, OR, Micropolitan Statistical Area. It is located on the south side of the Columbia River and is included in the eight-county definition of Eastern Oregon.
- Empty set (Wikipedia)
In mathematics, the empty set is the unique set having no elements; its size or cardinality (count of elements in a set) is zero. Some axiomatic set theories ensure that the empty set exists by including an axiom of empty set, while in other theories, its existence can be deduced. Many possible properties of sets are vacuously true for the empty set.