Final answer:
The relationship where one organism benefits at the expense of another, causing it harm, is called parasitism.
Step-by-step explanation:
The form of symbiosis where one partner benefits at the expense of the other, potentially causing harm and even death to the host, is known as parasitism. In this type of symbiotic relationship, the parasite derives benefit while the host is adversely affected. This is distinctly different from other types of symbiotic relationships such as mutualism, where both organisms benefit, and commensalism, where one organism benefits without affecting the other negatively. Another form, mentalism, involves one organism being inhibited or destroyed while the other remains unaffected.