Rules for writers, Tenth edition - Diana Hacker, Nancy Sommers 2021

Balance parallel ideas in a series
Balance parallel ideas
Clarity

If two or more ideas are parallel, they should be expressed in parallel grammatical form. Single words should be balanced with single words, phrases with phrases, clauses with clauses.

9a Balance parallel ideas in a series.

Balance all items in a series by presenting them in parallel grammatical form.

Headings

Headings on the same level of organization should be written in parallel form — as single words, phrases, or clauses.

PHRASES AS HEADINGS

✵ Safeguarding Earth’s atmosphere

✵ Charting the path to sustainable energy

✵ Conserving global forests

INDEPENDENT CLAUSES AS HEADINGS

✵ Ask the patient to describe current symptoms.

✵ Take a detailed medical history.

✵ Record the patient’s vital signs.

Lists

Lists are usually introduced with an independent clause followed by a colon. They are most readable when they are presented in parallel grammatical form. Like headings, lists might consist of single words, phrases, or clauses. The list in the following sentence consists of parallel noun phrases.

Renewable energy technologies include the following: hydroelectric power, solar power, wind energy, and geothermal energy.