Rules for writers, Tenth edition - Diana Hacker, Nancy Sommers 2021

Avoid is when, is where, and reason … is because constructions
Untangle mixed constructions
Clarity

Sentences with is when, is where, and reason … is because constructions are often ungrammatical or illogical and should be avoided. Grammatically, the verb is (as well as are, was, and were) should be followed by a noun or an adjective, not by an adverb clause beginning with when, where, or because.

Logically, the words when, where, and because suggest relations of time, place, and cause — relations that do not always make sense with is, are, was, or were.

EXERCISE 11-1

Edit the following sentences to untangle mixed constructions. Possible revisions appear in the back of the book.

a. Using surgical gloves is a precaution now worn by dentists to prevent contact with patients’ blood and saliva.

b. A physician, the career my brother is pursuing, requires at least ten years of challenging work.

c. The reason the pharaohs had bad teeth was because tiny particles of sand found their way into Egyptian bread.

d. Recurring bouts of flu among team members set a record for number of games forfeited.

e. In this box contains the key to your future.