Final answer:
In the sentence provided, "good" is used as a noun, indicating the welfare or benefit of Elizabeth's subjects.
Step-by-step explanation:
When Elizabeth says, "My heart was never set on worldly goods, but only for my subjects' good," the word "good" functions as a noun. In this context, "good" refers to the well-being or benefit of her subjects, which is a thing rather than a quality or description, making it a noun. As a noun, "good" indicates what Elizabeth's heart was set upon, namely, the prosperity or advantage of her subjects rather than material possessions or worldly goods.
Learn more about Parts of Speech - Good