Between vs Among: Two Items, Groups, and Individual Relationships

The rule “between for two, among for three or more” is only a first approximation. English also uses between with more than two participants when the relationships are considered individually.

Negotiations between the five departments is natural because each department is a distinct party. There was agreement among the staff treats the staff as a group.

Think in relationships, not arithmetic

Use between for distinct points, choices or parties; use among for membership or distribution within a group.

If prepositions generally cause difficulty, review prepositions of place and movement. In formal writing, do not choose among merely because the noun is plural; ask how the relationship is conceptualised.