edition the form in which a text (especially a printed book) is published
electron shell a grouping of electrons surrounding the nucleus of an atom; "the chemical properties of an atom are determined by the outermost electron shell"
ethnic group,
ethnos people of the same race or nationality who share a distinctive culture
race a contest of speed; "the race is to the swift"
association the act of consorting with or joining with others; "you cannot be convicted of criminal guilt by association"
swarm,
cloud a group of many things in the air or on the ground; "a swarm of insects obscured the light"; "clouds of blossoms"; "it discharged a cloud of spores"
subgroup (mathematics) a subset (that is not empty) of a mathematical group
Grouping is form of hierarchical knowledge representation, similar to mind mapping, concept mapping and argument mapping, all of which need to observe at least some of the principles of grouping. The principles of grouping include MECE (mutually exclusive and collectively exhaustive), levels of abstraction and horizontal and vertical congruence.