A single molecule. If you split that up, it will no longer be water.
Smallest amount.
c
"Least" means smallest in amount, extent, or significance. It is the antonym of "most".
0
Cd
Little
The smallest quantity of an element is an atom.
It is the minimum value of the set.
The smallest amout of rainfall is zero-- none at all.
0.08 is the smallest.
micro
quantum