You can make your sentences clearer and better by using parallel structures. That means if you are listing items, you have to ensure that they are in the same parts of speech. Clauses, too, need to be balanced.

• I have to cook, wash and clean.

This sentence is parallel because it uses the same construction (infinitive) after have.

Now consider the sentence I have to cook, washing and cleaning.

This sentence is not parallel because we use both infinitives and –ing forms in the same construction.

• She likes dancing, singing and acting. (Parallel)
• She likes to dance, singing and acting. (Not Parallel)

More examples are given below.

• Susie likes to play the piano and sing Christmas carols. (Right)
• She likes to play the piano and singing Christmas carols. (Wrong)

• Rahul did his homework, had a shower and went to play in the garden. (Right)
• Rahul did his homework, had a shower and had gone to play in the garden. (Wrong)

Rules of parallelism

Parallelism is all about balancing nouns with nouns, verbs with verbs, adjectives with adjectives, infinitives with infinitives and clauses with clauses.

• My mother likes cooking and knitting. (Here we balance two –ing forms.)
• He is tall, dark and handsome. (Here we balance three adjectives.)

Parallelism is also used with elements being compared.

• She likes reading books more than watching TV.