between

prep. & adv.
—prep.
1 a at or to a point in the area or interval bounded by two or more other points in space, time, etc. (broke down between London and Dover; we must meet between now and Friday). b along the extent of such an area or interval (there are five shops between here and the main road; works best between five and six; the numbers between 10 and 20).
2 separating, physically or conceptually (the distance between here and Leeds; the difference between right and wrong).
3 a by combining the resources of (great potential between them; between us we could afford it). b shared by; as the joint resources of (pound5 between them). c by joint or reciprocal action (an agreement between us; sorted it out between themselves).
Usage:
In sense 3 with reference to more than two people or things is established and acceptable (e.g. relations between Britain, France, and Germany).
4 to and from (runs between London and Sheffield).
5 taking one and rejecting the other of (decide between eating here and going out).
—adv. (also in between) at a point or in the area bounded by two or more other points in space, time, sequence, etc. (not fat or thin but in between).
Phrases and idioms:
between ourselves (or you and me) in confidence. between times (or whiles) in the intervals between other actions; occasionally.
Etymology: OE betweonum f. Gmc (as BY, TWO)