Parallelism (rhetoric)

Parallelism is a rhetorical device that compounds words or phrases that have equivalent meanings so as to create a definite pattern. This structure is particularly effective when "specifying or enumerating pairs or series of like things". A scheme of balance, parallelism represents "one of the basic principles of grammar and rhetoric".
Parallelism as a rhetorical device is used in many languages and cultures around the world in poetry, epics, songs, written prose and speech, from the folk level to the professional. It is very often found in Biblical poetry and in proverbs in general. 
Examples.
The following sentences and verses possess "similarity in structure" in words and phrases:
In the quote above, the compounded adjectives serve as parallel elements and support the noun "law".
In the above quote, three infinitive verb phrases produce the parallel structure supporting the noun "purpose". Note that this rhetorical device requires that the coordinate elements agree with one another grammatically: "nouns with nouns, infinitive verb phrases with infinitive verb phrases and adverb clauses with adverb clauses." 
When the coordinate elements possess that same number of words (or in the example below, the same number of syllables) the scheme is termed isocolon:
Synonymous parallelism in which one couplet expresses similar concepts can also be combined with antithetical parallelism in which a second couplet contrasts with the first. For example, synonymous and antithetical parallelism occur in Revelation 22:11:
Forms.
Parallelisms of various sorts are the chief rhetorical device of Biblical poetry in the tristich and in multiples of distich parallels and also in the poetry of many other cultures around the world, particularly in their oral traditions. Robert Lowth coined the term "parallelismus membrorum" (parallelism of members, i.e. poetic lines) in his 1788 book, "Lectures on the Sacred Poetry of the Hebrew Nation". Roman Jakobson pioneered the secular study of parallelism in poetic-linguistic traditions around the world, including his own Russian tradition. 
Chinese and Vietnamese classical poetry and prose have frequently made use of parallelism. Conversations between learned men in many cases involved exchanging single as a form of playing with words, as well as a kind of mental duel. In a parallel couplet, not only must the content, the parts of speech, the mythological and historico-geographical allusions, be all separately matched and balanced, but most of the tones must also be paired reciprocally. Even tones are conjoined with inflected ones, and vice versa.
Parallelisms in artistic speech are common in some languages of Mesoamerica, such as Nahuatl (Aztec). It has also been observed in a language of Indonesia (that Fox imprecisely referred to as "Rotinese") and Navajo. Other research has found parallelisms in the languages of the Ural-Altaic area (including Finnish-Karelian folk poetry and the epics and songs of the Turkic and Mongolian peoples) and Toda, suggesting wider distribution among Dravidian languages.
In proverbs.
Parallelisms in proverbs are very common in languages around the world. Parallel structures in short passages such as proverbs help direct the listener or reader to compare the parallel elements and thereby more easily deduce the point. 