Parallelism, also known as parallel structure, is the expression of ideas in the same grammatical form in order to create balance and clarity in a sentence.
Make sure the nouns are paired with nouns, verbs are paired with verbs, etc, and that the tenses and forms match.
✗ I enjoy walking, swimming, and to run.
✓ I enjoy walking, swimming, and running.
✗ I can water the grass, the plants, and I can water the vegetable tree.
✓ I can water the grass, the plants, and the vegetable tree.
Coordinating conjunctions are for, and, not, but, or, yet, so. Use parallelism in elements joined by coordinating conjunctions.
✗ She hates to read, but likes watching TV.
✓ She hates reading, but likes watching TV. OR She hates to read, but likes to watch TV.
✗ I have to decide between doing laundry, washing the dishes, or to vacuum the house.
✓ I have to decide between doing laundry, washing the dishes, or vacuuming the house.
Correlative conjunctions are pairs of conjunctions that show relationships between different parts of the sentence.
✗ He either could go to the baseball game or he could see his friend perform.
✓ He could either go to the baseball game or see his friend perform.
✗ She was neither willing nor was she able to help out.
✓ She was neither willing nor able to help out.
✗ I like to paint better than drawing.
✓ I like painting better than drawing.
✗ I go to the gym more than jogging.
✓ I go to the gym more than I jog.
However, if the sentence previously includes a which or who subordinate clause that can be expressed in parallel structure, using and is okay.
✗ James Patterson is a well-known author, and who has written many books.
✓ James Patterson is a well-known author who has written many books.
✓ The guest speaker was Malcolm Gladwell, who has written many self-help books and who is a Canadian journalist.
✗ To fail is never trying.
✓ To fail is to never try.