Definition - Using a similar structure in a series of related words, phrases, or clauses.

Example -
Life is tough, fish are cheap, death is abundant, but salmon is best.

Etymology -
The word derives from the Greek para allelois, beside one another (from para, beside + allelois, each other).

Oxford English Dictionary -
Its first citation in this sense is from 1778:
"The correspondence of one Verse, or Line, with another, I call Parallelism. When a Proposition is delivered, and a second is subjoined to it, or drawn under it, equivalent, or contrasted with it, in Sense; or similar to it in the form of Grammatical Construction."
( R. Lowth Transl. Isaiah Prelim. Diss. 10)

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