Microsoft Word’s grammar check alerts you when you repeat a word, but is repeating a word always wrong? Bonnie Trenga, author of The Curious Case of the Misplaced Modifier, says no. Here are several examples to illustrate when it’s perfectly fine to repeat a word.
A common double is “had had.” Take this sentence: “I have had too many chocolates today.” That sentence is in the present perfect tense. You use that tense when you’re talking about a past action that is continuing into the present.
To put the chocolate sentence in the past tense, we’d use past perfect tense, which uses “had” plus the past participle, as in “had had” and “had gone.” So in the sentence “I had had too many chocolates, so I was too full to eat dinner yesterday,” two things happened in the past. First was eating chocolates; second was trying to eat dinner.
Another doubling up occurs with the verb “to be.” This phenomenon is sometimes called the “double is.” Example: “The problem is is that it’s raining,” the subject of the sentence is “the problem”; therefore, we need only one “is.” There is, however, a case when two “is” verbs in a row is more defensible. “What he is is a complete jerk.” We use such sentences when we want to emphasize our point.
The bottom line: Sometimes you double words in the normal course of creating a sentence. But if you don’t like them, go ahead and reword your sentence.
— Adapted from “When Are Double Words OK?,” Bonnie Trenga, Grammar Girl.