among / between
Two prepositions of position, sharing, and relationship.
Use between for one-to-one relations, even when more than two parties are named: the border between France, Germany, and Switzerland; talks between the five firms. Use among when the relationship is collective or the members are not taken pairwise: a custom among sailors; divide the work among the staff. The old “between for two, among for more than two” rule is too tight. Two items still take between: between you and me.
Examples
UseThe estate was split between the three children. (each share is distinct)
UseThere was little trust among the three children. (the group as a whole)
UseChoose between the two proofs.
AvoidChoose among the two proofs.