Definition:

In a sentence, a balanced arrangement of two roughly equal parts: a form of parallelism.

By convention, items in a paired construction appear in parallel grammatical form: a noun phrase is paired with another noun phrase, an -ing form with another -ing form, and so on. Failure to express such items in similar grammatical form is called faulty parallelism.
See Examples and Observations, below.

Also see:

• Balanced Sentence
• Antithesis
• Chiasmus
• Comparative Correlative
• Coordinating Conjunctions
• Coordinating Words, Phrases, and Clauses
• Coordination
• A Definition of a Gentleman, by John Henry Newman
• Dirimens Copulatio
• Parallel Structure

 

Examples and Observations:

• "Major league baseball has been thrown into the Cuisinart of big-time sport, a whirring blur of money and celebrity, personality and PR, moveable franchises and replaceable stars, outsize in their talent but less and less distinguishable from one another or from the rest of the entertainment repast."
  (Roger Angell, "Lost and Found." The Perfect Game: America Looks at Baseball, ed. by Elizabeth V. Warren. American Folk Art Museum, 2003)
• "I believe that man will not merely endure: he will prevail."
  (William Faulkner, Nobel Prize Acceptance Speech, Dec. 10, 1950)
• "Certainty of death, small chance of success: what are we waiting for?"
  (John Rhys-Davies as Gimli in The Lord of the Rings: The Return of the King, 2003)
• "So let us begin anew--remembering on both sides that civility is not a sign of weakness, and sincerity is always subject to proof. Let us never negotiate out of fear, but let us never fear to negotiate."
  (President John Kennedy, Inaugural Address, Jan. 20, 1961)

• "To the people of poor nations, we pledge to work alongside you to make your farms flourish and let clean waters flow; to nourish starved bodies and feed hungry minds."
  (President Barack Obama, Inaugural Address, Jan. 20, 2009)
• "One might ponder the melancholy question whether it does take misfortune and great tension, national agitation and even calamity, to arouse and inspire film-makers to dare radical leaps ahead and explode devastating expressions."
  (Bosley Crowther, The Great Films: Fifty Golden Years of Motion Pictures. Putnam, 1971)
• "Something momentous was bound to happen soon. The entire collective unconscious could not be wrong about that. But what would it be? And would it be apocalyptic or rejuvenating? A cure for cancer or a nuclear bang? A change in the weather or a change in the sea?"
  (Tom Robbins, Still Life With Woodpecker. Random House, 1980)
• "[R]emember how strong we are in our happiness, and how weak he is in his misery."
  (Charles Dickens, A Tale of Two Cities, 1859)
• Pairings for Emphasis
  "When parallel ideas are paired, the emphasis falls on words that underscore comparisons or contrasts, especially when they occur at the end of a phrase or clause:

  We must stop talking about the American dream and start listening to the dreams of Americans. --Reubin Askew"

  (Diana Hacker and Nancy Sommers, A Writer's Reference, 7th ed. Bedford/St. Martin's, 2011)
  
  "The obvious strength of a paired construction is in its balance and seeming thoughtfulness. When you use a paired construction you are demonstrating that you are capable of planning ahead in a mature fashion, and are not merely putting down words as they pop into your mind."
  (Murray Bromberg and Julius Liebb, The English You Need to Know, 2nd ed. Barron's, 1997)