A common writing fault is faulty parallelism.
In writing, parallelism is a similarity of construction of adjacent word groups. Faulty parallelism results when words, phrases, or clauses are mismatched.
Here are some examples of faulty parallelism:
Hiking is more fun than to swim.
“Hiking” is a verbal noun. “To swim” is an infinitive.
Hiking is more fun than swimming.
To hike is more fun than to swim.
Sandra Bullock is beautiful and has intelligence.
“Beautiful” is an adjective; “has intelligence” is a clause.
Sandra Bullock is beautiful and intelligent.
Sandra Bullock has beauty and intelligence.
Even though we have had peaceful protest, there has been protest that was violent, even today.
This sentence from a student essay about a tradition of violence in the United States has several problems. The first clause begins with a true subject, “we,” while the second clause begins with “there.” The delayed subject of the second clause is “protest.” Having “protest” as the object of a verb in the first clause and the subject of the verb in the second clause is awkward. More imbalance results from the mix of past and present verb tenses and the tacked-on phrase “even today.” “Even though” seems to call for a stronger contrast than what follows.
Even though we have had peaceful protests, violent protests have been common and continue today.
The nightly news is full of stories about missing children or stories that someone tried to abduct some children at a bus stop.
This example is also from a student essay. The structural imbalance results from the fact that the first “story”–“stories about missing children”– is qualified by an adjective phrase, while the second “story”–“stories that someone tried to abduct some children at a bus stop”– is qualified by an adjective clause.
The nightly news is full of stories about missing children and child abductors.
The nightly news is full of stories about children who have disappeared from their homes or who have been abducted at bus stops.
A recent Apple ad for the iPad contains an example of faulty parallelism in the list of words interspersed with a series of screenshots:
All but one of the words is a descriptive adjective. “Learning” is a verbal noun. The adjective that would fit with the other adjectives is “educational.” Perhaps the copywriter felt that the word “educational” is too stodgy for an Apple ad targeting fun-loving consumers.