Either ... or ...
The construction either ... or ... is used to express a disjoint union or enumerate individuals of a given concept.
Those examples show how to the either ... or ... construction.
Example: The concepts of child, young thing, middle age thing and old thing are all pairwise disjoint. Their union is a person.
Something is a person if-and-only-if-it-f is a child, is a young-thing, is a middle-age-thing or is an old-thing.
Example: Enumerates individuals of a concept.
Something is a my-birthday-guests if-and-only-if-it is either John, Mary or Bill.