Faulty parallelism occurs when the elements put into pairs and
series "go in different directions" because they do not have the same form. In other words,
nouns should be coordinated with nouns, verbs with verbs, adjectives with adjectives,
adverbs with adverbs, phrases with phrases, and clauses with clauses. To check for faulty
parallelism it is often useful to underline or otherwise mark parallel (coordinate)
elements. Following are three common types of faulty parallelism: faulty pairs, the
shifted series, and the "and who" or "and which" construction.
from The SDSU Writing Center
Assisted by Leigh Averett