1. In anatomy, especially in ancient Greece, a group of soldiers that attacked in close formation, protected by their overlapping shields and projecting spears.
2. A group of people, animals, or objects that are moving or standing closely together.

Phalanx originally referred to the whole row of finger joints, and this was so called because the arrangement suggested a battle array (orderly grouping or force).

It apparently is based on an ancient Greek battle formation of infantry fighting in close ranks; then it became Latin phalanx, or was borrowed directly from Greek phalanx, a line of battle; and then "finger bone" or "toe bone". Now phalanx refers to any one of those finger or toe bones.

In anatomy, the phalanx is a long bone of the digits of the hand and foot, usually with three segments in each digit, except for the thumb and great toe.

The segments are referred to as the proximal, middle, and distal segments; the thumb and great toe have only proximal and distal segments.

Each bone has a base, a body or shaft, and a head. The proximal phalanx is the longest of the three bones.