Use between when the things are separate and individually in play, however many there are: "the differences between the four dialects". Use among when the group is an undifferentiated mass: "the rumour spread among the staff". The old "between is only for two" rule is an oversimplification — "a deal between the six unions" is perfectly correct.
What the rule actually is
Most of us were taught that between takes two things and among takes three or more. It is a serviceable rough guide, and it is wrong often enough to be worth replacing.
The genuine distinction is about how the group is being viewed. Between treats the members as individually identifiable, each one in a one-to-one relationship with the others. Among treats them as a collective, with no particular member picked out.
- Trade agreements between the twelve member states. — twelve, but each state is a distinct party.
- The news travelled quickly among the crowd. — the crowd is a mass, not a set of named parties.
When between is right
- Relationships between named parties: the gap between rich and poor; a dispute between the three neighbours.
- Physical position where you can identify the boundaries: The cottage sits between the road and the river.
- Ranges: between 1990 and 2004; between five and ten centimetres.
- Distinguishing: I can't tell the difference between them.
When among is right
- Being surrounded by an indistinct group: He was standing among the reeds.
- Distribution across a body of people: The estate was divided among her nephews.
- Prevalence: Unemployment is highest among under-25s.
- Membership: She was among the first to arrive.
The test
Ask whether you could name and separate the items. If your sentence could be rewritten as a series of pairs — this one with that one, that one with the other — use between. If the group is a blur you are dropping something into or moving through, use among.
A quick second check for physical position: between the trees means you can picture the specific trees on either side; among the trees means somewhere in the wood.
Amongst, and other loose ends
Amongst means exactly the same as among. It is more common in British writing and sounds slightly more formal or literary; it is not more correct, and American editors tend to strike it. Pick one and be consistent.
One genuine error to watch: after between, use object pronouns. It is between you and me, never between you and I — a case where trying to sound careful produces the mistake.
Frequently Asked Questions
Is it "between you and I" or "between you and me"?
Between you and me. Between is a preposition, so the pronouns after it take the object form — the same reason we say "between us", not "between we".
Can between be used for more than two things?
Yes. When the items are distinct parties in a relationship, between is correct at any number: "the border between the three countries", "choose between the five options".
Is "amongst" wrong?
No, it is a standard variant of among with the same meaning. It reads as more formal and is more usual in British English; American style guides generally prefer among.