Careful writers ensure that items in a list are parallel with one another in both meaning and form. That is, all items must be both logically and grammatically similar; when they are, the information is more coherent and easier to absorb. Today, we’re looking specifically at parallel structure with vertical lists, those that use bullets, numbers, or letters.

Parallel Meaning

Some writers think anything related to a given topic is fair game in a list, but they risk confusing their readers when not all items in their list are logically consistent.

Look at this illogical (and grammatically unparallel) list:

Widgets for the World developed a marketing campaign to reach sales objectives:

  • To grow our share of the US widget market by 10% over the next year.
  • We want to increase widget sales in the EU by 5%.
  • To open widget markets in Canada.
  • To launch the campaign on April 10.
  • Emily Jones will oversee this campaign.

We tell readers we are going to list the objectives of a marketing campaign, but then we illogically include in that list the kick-off date and the point person.

Parallel Form

To be parallel, every item in a list also needs to share the same grammatical form. The Widgets list includes three infinitive phrases (starting with to grow, to open, and to launch) but also two sentences, so it’s not grammatically parallel.

A parallel list may consist of all single words of the same part of speech (all nouns, all adjectives, all verbs, etc.), all phrases of the same structure (all infinitive phrases, all gerunds, all prepositional phrases, etc.), all subordinate clauses, or all independent clauses (complete sentences). Here are some examples:

Single words (here, all nouns):

College students need funds for

  • books,
  • transportation, and
  • entertainment.

Noun phrases:

Businesses are better able to retain employees who are given

  • flexible schedules,
  • comprehensive health care benefits, and
  • substantial retirement benefits.

Other phrases of the same structure (here, gerund phrases)

Let your doctor know if your child is not performing any of the following tasks at the same rate as other children the same age:

  • identifying shapes, colors, and familiar objects;
  • speaking or putting together phrases and sentences; or
  • following directions and remembering information.

Subordinate clauses (here, relative clauses):

The press noted that the jury consisted solely of people

  • who had completed at least one year of education beyond high school,
  • who had incomes in excess of $60,000, and
  • who had lived in the Houston area for at least ten years.

Independent clauses (complete sentences):

Cybil’s speech contained three clichés:

  • “A watched pot never boils.”
  • “Look before you leap.”
  • “The early bird gets the worm.”

Lists that display both logical and grammatical parallelism not only appear more polished but enhance reader comprehension.

In this article we have focused on parallel structure with vertical lists. Lists that appear within a sentence or paragraph must also be parallel–a topic we will address in a future article. For more information about (and many examples of) vertical lists, including punctuation and capitalization conventions, go to this article.