Parallel Structure

• Joshua likes to bike, to swim, and to eat.

All of the words after the verb likes take the infinitive form.

• Joshua likes to bike, to swim, and eating.

While to bike and to swim are infinitives, eating is a gerund.

• Yuki’s career goals include acting, singing, and dancing.

All of the words after include take the gerund form.

• Yuki’s career goals include acting, singing, and to dance. 

While acting and singing are gerunds, to dance is an infinitive.

🚫 Professor Smith, the biology instructor, has said that to succeed in his course, students must attend every class, must remain attentive during lectures, and take strong notes.

This sentence does not follow parallel structure.  The must in front of remain is not required.

✅ Professor Smith, the biology instructor, has said that to succeed in his course, students must attend every class, remain attentive during lectures, and take strong notes

Here’s another example:

🚫 The high school student, like many around her age, enjoys playing sports, going to the beach, and to read.

This sentence does not follow parallel structure, since two items take the gerund form and one takes the infinitive form. The same form must be used for each item:

✅ The high school student, like many around her age, enjoys playing sports, going to the beach, and reading.

The ACT will give you a conjunction (and, but, or, yet, so, for, etc.) or word pair, and your mission is to make sure that the words on either side of the conjunction/word pair follow parallel structure.

Common word pairs

• Neither X nor Y
• Both X and Y
• Not only X but also Y 
• Either X or Y 
• Just as X, so Y 
• Not so much X as Y 
• At once X and Y 

🚫 The surfing lessons, taken daily with a qualified instructor, will increase your confidence in the ocean and improvement will be observed in your skills on the board.

The second half of the sentence—the part after “and”—does not follow parallel structure. It should read:

✅ The surfing lessons, taken daily with a qualified instructor, will increase your confidence in the ocean and improve your skills on the board.

🚫 The iPhone can not only recognize your fingerprint to unlock the home screen but also it can be used to look up that day’s weather​.

This sentence does not have parallel structure, because the words on each side of the word pair (not only…but also) do not follow the same structure. It should read:

✅ The iPhone can not only recognize your fingerprint to unlock the home screen but also look up that day’s weather.

Find out what type of pattern the sentence follows and make sure all parts of the sentence follow that same pattern. 

Find where the pattern begins and read each part separately.

Let’s take a look at the previous examples and try each item separately with the subject and verb.

The surfing lessons will increase your confidence in the ocean and improvement will be observed in your skills on the board.

✅ The surfing lessons will increase your confidence in the ocean

🚫 The surfing lessons will improvement will be observed in your skills on the board.  

The iPhone can not only recognize your fingerprint to unlock the home screen but also it can be used to look up that day’s weather​.

✅ The iPhone can not only recognize your fingerprint to unlock the home screen

🚫 The iPhone can it can be used to look up that day’s weather​.

Trying each item with the subject and verb makes it even clearer when the items are not parallel.