Boyan is an uncommon and specific word used within the Eastern Slavic tradition, referring to a particular type of epic or heroic poem. However, there are several synonyms that may be used to describe similar types of traditional storytelling or literature from other cultures. In the Middle East, for example, the term "qasida" is often used to describe a similar long narrative poem. In Japanese literature, there is the term "kakemono" which refers to a long, scroll-like painting often used to tell a story. Other words that may be used interchangeably with boyan could include ballad, saga, epic, or chronicle, depending on the specific cultural context.