a. In or through the position or interval separating: between the trees; between 11 o'clock and 12 o'clock.
b. Intermediate to, as in quantity, amount, or degree: It costs between 15 and 20 dollars.
2. Connecting spatially: a railroad between the two cities.
3. Associating or uniting in a reciprocal action or relationship: an agreement between workers and management; a certain resemblance between the two stories.
4. In confidence restricted to: Between you and me, he is not qualified.
a. By the combined effort or effect of: Between them they succeeded.
b. In the combined ownership of: They had only a few dollars between them.
6. As measured against. Often used to express a reciprocal relationship: choose between riding and walking.
In an intermediate space, position, or time; in the interim.
In an intermediate situation: My roommates disagreed and I was caught in between.
in between times
During an intervening period; in the meantime: has written several books and teaches in between times.
[Middle English bitwene, from Old English betwēonum; see dwo- in the Appendix of Indo-European roots.]
Usage Note: The –tween in between comes from the same Indo-European root that gave us two, twain, and duo, and the –mong of among comes from an Old English word that meant "crowd" or "throng." It is thus unsurprising that a traditional rule requires between to be used only for sentences involving two items and among for sentences involving more than two. Indeed, in sentences involving two items, no rule is needed; native English speakers spontaneously use between (as in the differences between [not among] karate and judo). But when there are more than two items, practice is mixed. Many careful writers observe a more subtle distinction, using among when the sentence refers to the entities collectively or as a mass, as in There were many outstanding players among the teams in the quarterfinal round or A thistle is growing among the roses, but preferring between when the sentence refers to relationships involving particular pairs of entities from within the group, as in We haven't yet assigned the matchups between teams in the quarterfinal round or I have sand between my toes. In such sentences, the twoness of between has not, so to speak, been lost in the crowd—the pairings within the larger group are important to the meaning of the sentence and thus influence the writer's choice of preposition.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendicies
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.