dom

The root dom is really three Latin siblings braided together, all radiating from the idea of a household and the person who runs it.

domus meant "house, home" — the physical building and the family inside it. From this comes the most everyday member of the family: domestic (belonging to the house) — first "of the household," then "of the home country" (domestic flights, domestic policy). A domicile is your legal house, your official residence. And dome is the surprising one: through Italian duomo (cathedral, literally "the house [of God]"), the word came to mean the great rounded roof that crowns such a building.

dominus meant "master, lord" — the man who rules the house (the domus). Once you have a master, you have a whole vocabulary of power:
- domin + -ate → dominate: to be master over
- domin + -ant → dominant: holding the master's position
- domin + -ion → dominion: the territory and authority of a lord
- domain comes through Old French from dominium (lordship) — the land a lord controls, later any "field" you command (the domain of physics, a website domain)
- pre- (before, above) + dominant → predominant: ruling over the rest
- domineering keeps the harsh edge: bossing others like a tyrant

The most startling member is danger. It travelled through Old French dangier, from Vulgar Latin dominiarium — "the power of a lord." To be "in someone's danger" originally meant to be in his power, at his mercy. Being at the mercy of a powerful man is risky, so over the centuries the meaning slid from "a lord's power" to plain "risk, peril." That is why endanger (put into danger) and endangered (species at risk) ultimately go back to a Roman master of the house.

domāre meant "to tame" — to bring a wild thing under control, into the household. From it: domesticate (to tame animals or cultivate plants for human use) and domestication. Taming is just rule applied to nature.

Finally, kingdom and freedom look like they belong here, but their -dom is the Germanic suffix meaning "state, realm, condition" (king + dom = the realm of a king; free + dom = the state of being free). These two words took the Germanic road into English rather than the Latin one, so keep them apart from domus.

The pattern to remember: domus is the house, dominus is who runs it, domāre is taming the wild to fit it — and "power over a place" is the thread tying domestic, domain, dominate, and even danger together.