There is not a drop of water left.

I felt a drop of rain on my head.

Private charity is only a drop in the bucket.

We have not had a single drop of rain for two weeks.

One drop of this poison is enough to kill 160 people.

One drop of the poison is enough to kill 160 people.

She turned away from me to hide a tear that had begun to fall down her cheek.

A drop in the bucket.

OK, just a drop.