Which statement among the following rightly defines an epithet?

The correct option is: An adjective/adjectival phrase used to define a characteristics quality or attribute of some person or thing.

Understanding Epithets:
An epithet is a literary and rhetorical device. The word itself comes from the Greek epithetos, which means "added" or "attributed". It is a descriptive word or phrase (often an adjective or noun phrase) that accompanies or replaces a name to point out a prominent feature, personality trait, or physical characteristic of a person, place, or object. For example, in the historical name "Alexander the Great," the phrase "the Great" serves as the epithet. Similarly, in Homer's epic poetry, characters and objects are regularly accompanied by standard descriptive phrases, such as "swift-footed Achilles" or "rosy-fingered Dawn." These help to reinforce key qualities in the mind of the audience.

Analyzing the Other Options:
1. "An adjective / adjectival phrase that condemns the protagonist of a story/novel": This is incorrect because epithets are not restricted to negative descriptions or condemnation, nor are they limited only to protagonists.
2. "An adjective/ adjectival phrase suited for inscription on a tomb or memorial": This option describes an epitaph, which is a short text honoring a deceased person, often inscribed on a tombstone. While the words sound similar, their meanings are distinct.
3. "A rhetorical figure by which the same word or phrase is repeated at the end of successive lines.": This describes epistrophe (also known as epiphora), which is a stylistic repetition device, not an adjectival description.