What word describes the relationship between fleas and their hosts?

The relationship between fleas and their hosts is called parasitism.

Here's why:

* Fleas benefit: They feed on the blood of their host, which is essential for their survival.

* Hosts are harmed: Fleas can cause itching, skin irritation, and even transmit diseases.

This one-sided relationship where one organism benefits at the expense of the other is the defining characteristic of parasitism.