Good writing sounds good to the ear.

The sentence “Mary likes hiking, swimming and to ride a bicycle” is understandable; most readers will know exactly what it means.

However, the sentence feels uneven because the three activities do not share the same grammatical shape.

“Hiking” and “swimming” are -ing forms, while “to ride” shifts suddenly to an infinitive. Revising the sentence in this way, “Mary likes hiking, swimming and cycling,” is smoother because each item follows the same pattern.

This is called a parallel structure. It helps a sentence sound balanced, clear and natural.

Good writing is not only just about being correct; it is also about rhythm.

When sentences are read aloud, repeated patterns guide the ear, reduce awkwardness and make the message more pleasing to hear.