atom

Meronyms: proton, neutron, electron

Towards the following morning, the thermometer fell to 5°; and at daylight, there was not an atom of water to be seen in any direction.

"Doctor, tell me one word more," said Theodore, quivering with suppressed emotion. "How do you think it will end?" / "I have hardly the faintest atom of hope," answered this honest, earnest man.

In a Venn diagram, an atom is depicted as an area circumscribed by lines but not cut by any line.