0 How is the phrase "that is," meaning "namely," properly used and punctuated in the following sentence:02br 02br 00"In support of my argument, I submit, as I did previously, that Report IV is flawed for the same reason that Reports I through III were flawed, 01b00that is02b00, it was not signed by a supervisor."02br 02br 00A colleague asked me about this, and I told her "that is" is idiomatic and she could not go wrong surrounding it with commas as above, placing a semi colon before it and a comma after it, or omitting the trailing comma (but using a preceding comma or semi). A quick survey of Batlett's quotations (for synonyms "namely" and "viz.," since searching for "that is" is useless) shows that all of these iterations are in common usage. However, I am troubled and would like a more expert opinion. 02br 02br 00I originally considered "that is" to function as an adjectival phrase modifying "reason." Now, though, I think it looks more like a conjunctive adverb. But, I am leery of labeling something an adverb just because it doesn't seem to fit anywhere else. Does anyone care to offer an opinion? If it is a conjunctive adverb, must it be preceded by a semi colon or can it, like "otherwise," be preceded by a comma?0-
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02br 02br 01i 00Quirk et al02i 00 call that is an 'appositional conjunct', and a nonrestrictive one at that. In another section they indicate that the convention is to precede01b 01i 00 that is02i 02b 00 with a semicolon; however, among their examples are several in which it is preceded by an m-dash. They also state, interestingly, that it may be preceded by a comma if the following text is a phrase rather than a clause.
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0Hello Alex, and welcome to English Forums.02br 02br 01i00Quirk et al02i00 call that is an 'appositional conjunct', and a nonrestrictive one at that. In another section they indicate that the convention is to precede01b01i00 that is02i02b00 with a semicolon; however, among their examples are several in which it is prec