According to Donald Parry, parallelism is universally recognized as the characteristic feature of biblical Hebrew poetry. (p. i) Apparently, the prophets and writers of the scriptures employed the repetition of alternating parallel lines for the purpose of reinforcing their teachings and doctrines. (p. x)
When a group of three or more words, similar in sense but not identical in meaning, come together in a verse or passage with characteristics which parallel one another, this is called synonymia, or "synonymous words." (p. xlix) A good example of Synonymia is found in Mormon 8:39:
Why do ye adorn yourselves with that which hath no life,
and yet suffer the hungry,
and the needy,
and the naked,
and the sick,
and the afflicted.
[Donald W. Parry, The Book of Mormon Text Reformatted according to Parallelistic Patterns, p. 448]