between v. among

Prescriptive grammarians hold that between is used when discussing 2 entities, and among is used when discussing more than 2 entities. ‘Mesopotamia was located between the Tigris and Euphrates rivers’, but ‘Responsibility for excavating the site was divided among the 4 archaeologists.’ This belief is based more on etymology than usage, and while it often works, it’s ultimately specious.

Between deals with relations of discrete things, and among deals with collective or vague relations. The interior of a triangle is the region between (not among) its 3 sides, and it’s acceptable to say either, ‘The duck swam among (or between) the reeds’. In the sentence, ‘The bomb landed between the houses’, it’s clear, regardless of the number of houses, that while the bomb struck in their vicinity, none of the houses was directly hit. In, ‘The bomb landed among the houses’, the houses are being regarded collectively, and whether any one house was struck is ambiguous.

Grammar Girl on between v. among

Motivated Grammar on between v. among

Answers.com usage note on between v. among