Parallelism, also known as parallel structure or parallel construction, refers to the repetition of the same grammatical form across multiple parts of a sentence. Parallel structure helps to create clarity, balance, and coherence in sentences and paragraphs. It can be applied to words, phrases, clauses, and even lists.

Not ParallelParallel
She likes cooking, reading books, and to go hiking.She likes cooking, reading books, and hiking.
The project aims to reduce costs, improve efficiency, and for increasing customer satisfaction.The project aims to reduce costs, improve efficiency, and increase customer satisfaction.
The manager instructed us to work hard, be patient, and persisting through challenges.The manager instructed us to work hard, be patient, and persist through challenges.

Parallel structure in a series

Use parallel construction when elements within a series carry an equivalent level of significance. These elements are typically connected by commas or semicolons, accompanied by the conjunctions “and” or “or.”

Parallel words

When listing single words in a series, they should follow the same grammatical form (noun, verb, adjective, etc.) to maintain parallelism.

Not ParallelParallel
She is smart, intelligent, and a hard worker.She is smart, intelligent, and diligent.
The project requires dedication, perseverance, and to focus.The project requires dedication, perseverance, and focus.
They bought apples, oranges, and grape.They bought apples, oranges, and grapes.

Parallel phrases

Phrases listed in a series should maintain the same structure and grammatical form.

Not ParallelParallel
He enjoys reading books, watching movies, and to play video games.He enjoys reading books, watching movies, and playing video games.
The company aims to increase revenue, reduce expenses, and for improving customer satisfaction.The company aims to increase revenue, reduce expenses, and improve customer satisfaction.
She learned to code, designing websites, and wrote a blog.She learned to code, design websites, and write a blog.

Parallel clauses

Clauses in a series should follow the same grammatical structure.

Not ParallelParallel
The team aims to increase sales, reducing costs, and customer satisfaction will improve.The team aims to increase sales, reduce costs, and improve customer satisfaction.
The coach instructed us to practice daily, giving our best, and that we never give up.The coach instructed us to practice daily, give our best, and never give up.
She hopes to graduate, finding a job, and will travel the world.She hopes to graduate, find a job, and travel the world.

Lists after a colon

Items in a vertical list following a colon should maintain parallel structure.

Not ParallelParallel
To succeed, you need: hard work, dedication, and having a positive attitude.To succeed, you need: hard work, dedication, and a positive attitude.
The meeting agenda includes: discussing the budget, to review last quarter’s sales, and proposals for new initiatives.The meeting agenda includes: discussing the budget, reviewing last quarter’s sales, and proposing new initiatives.
Qualities of a good leader are: vision, effective communication, and to inspire others.Qualities of a good leader are: vision, effective communication, and inspiring others.

Parallel construction in pairs

Employ parallel construction when a sentence presents a pair of interconnected concepts. Pairs can be joined by coordinating conjunctions like and, nor, but, or, and yet.

Not ParallelParallel
She likes reading books and to watch movies.She likes reading books and watching movies.
The team succeeded due to hard work and good planning.The team succeeded due to hard work and good strategy.

Parallel structure is also necessary when a pair of ideas are linked by correlative conjunctions such as not only…but also, either…or, and neither…nor.

Not ParallelParallel
He is not only a gifted artist but also a talented musician.He is not only a gifted artist but also a talented writer.
Neither did she study hard nor worked diligently.Neither did she study hard nor work diligently.

The same principle applies to pairs connected by a word of comparison like over, than, or as.

Not ParallelParallel
Writing is as challenging than running a marathon.Writing is as challenging as running a marathon.
She is more dedicated to her work than being a good leader.She is more dedicated to her work than to being a good leader.

Outlines and headings

Parallel structure is essential in outlines and headings to maintain consistency and clarity.

Not ParallelParallel
A. The Industrial Revolution 
1. Technological Advancements 
2. Rise of Factories 
3. Urbanization  
4. Environmental Consequences Emerged		A. The Industrial Revolution 
1. Technological Advancements 
2. Rise of Factories 
3. Urbanization 
4. Emergence of Environmental Consequences
B. Environmental Movements 
1. Early Conservationists 
2. Increased Public Awareness 
3. Legislation and Regulations 
4. Promoting Sustainability Practices		B. Environmental Movements 
1. Early Conservationists 
2. Increasing Public Awareness 
3. Enactment of Legislation and Regulations 
4. Promotion of Sustainability Practices
C. Current Challenges 
1. Climate Change 
2. Biodiversity Loss
3. Pollution of Air and Water 
4. Depletion of Natural Resources Continues		C. Current Challenges 
1. Climate Change 
2. Loss of Biodiversity
3. Pollution of Air and Water 
4. Continued Depletion of Natural Resources