5 Cases for Requiring a Comma Before a Sentence Tag

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A sentence tag is a word or phrase added to the beginning or end of a statement for emphasis or to provide more information. For the following sentences, I discuss the necessity of preceding end-of-sentence tags with a comma.

1. “I shouldn’t have been surprised really.”

Without a comma separating really from the rest of the sentence, the implication is that really is an adverb modifying how the writer should not have been surprised (really, as in factually, and the opposite of allegedly). However, its function is merely to emphasize the point: “I shouldn’t have been surprised, really.”

2. “I was in the other room at the time actually.”

This sentence indicates that the writer was in the other room in an actual manner, rather than figuratively, but that’s not the literal meaning. The writer has been challenged about his or her location when an incident occurred, and the intent, again, is to emphasize. A comma is required before actually to signal this distinction: “I was in the other room at the time, actually.”

The idea could also be conveyed with actually inserted elsewhere in the sentence (in descending order of elegance): “Actually, I was in the other room at the time” or “I was, actually, in the other room at the time” or “I was in the other room, actually, at the time.” (Note that not all adverbial tags are so flexible about location; try these variations in the first example, and you’ll see that really seems to feel right only as a concluding tag.)

3. “We did it all right.”

This sentence implies that the writer is evaluating a merely competent performance. With a comma inserted before “all right,” the implication is of emphasis on the fact of the accomplishment: “We did it, all right.”

4. “They offered a free pass to boot.”

Without a comma preceding “to boot” (which means “as a bonus”), the phrase appears to describe an action that is, thanks to the pass, complimentary. The comma signals that “to boot” is an appendage that idiomatically offers additional information: “They offered a free pass, to boot.”

5. “Geology has an impact on biology and vice versa.”

As written, this sentence seems to equate biology and vice versa as two things geology has an impact on. But “vice versa,” meaning “the opposite,” applies to the entire sentence preceding it, so it must be set off from the sentence: “Geology has an impact on biology, and vice versa.”