The items on a list must match. A non-parallel list can be unclear, difficult to read, and grammatically incorrect.
The stem is the start of a list, and every item on the list must finish the sentence perfectly.
I like to read, to write, and to go swimming.
(stem/like – mismatch/go swimming)
I like to read, to write, and to swim.The crowd outside the was loud, boisterous, and they were angry.
(stem/was – mismatch/they were)
The crowd outside the embassy was loud, boisterous, and angry.Now that he’s won the lottery, he is selling the house, plans to move to Italy, and will take the family with him.
(stem/he is – mismatch/plans to move – mismatch/will take)
Now that he’s won the lottery, he is selling the house, moving to Italy, and taking the family with him.