trib

The root trib begins with a head count. When Rome was founded, the people were said to be split into three founding groups — and Latin tribus (a tribe) is traditionally tied to trēs, 'three.' Whether or not that arithmetic is literally true, the important thing is what a tribus did: it was the unit by which Rome organized its citizens. Soldiers were levied by tribe, votes were counted by tribe, and — crucially — taxes and land were divided up and handed out tribe by tribe.

That administrative act gave Latin the verb tribuere: 'to allot, to assign, to give as each one's share.' This is the hinge of the whole family. Once you see trib as 'apportion / give,' the abstract words snap into place through their prefixes:

- dis- (apart, in different directions) + tribuere → distribute: hand out in many directions, divide among many. Its noun is distribution — the spreading-out itself.
- con- (together) + tribuere → contribute: each person gives their share into a common pot. The noun contribution is what you put in.
- at-/ad- (to) + tribuere → attribute: assign a quality to someone. (This branch is enriched under the tribut root.)
- re- (back) + tribuere → retribution: paying back what is owed — punishment as a returned share. (Also under tribut.)

The other half of the family kept the literal social meaning. tribe is simply the tribus itself, and tribal is its adjective: belonging to a tribe. Modern English has even loosened tribe into 'your people' — find your tribe means find the group you belong to. From the same Roman political world come tribune (an officer elected by and for the tribes — a tribunus plebis, protector of the common people) and tribunal (originally the raised platform where a tribune sat to judge, now any court).

So the family has one fork: where something is given out or shared (distribute, contribute, attribute, tribute), and where a group of people is named (tribe, tribal, tribune). Both trace back to the same Roman headcount.

One warning: tribulation looks like it belongs here but does not. It comes from Latin tribulum, a threshing-sledge that crushed grain (from terere, 'to rub, grind') — affliction as a 'grinding down.' Same spelling, unrelated root.