From Cambridge Dictionary:

I'll meet you in the city, that is, I will if the trains are running.

Is the sentence grammatically correct? In my knowledge, only FANBOYS(for,and,but...) can lead independent clauses.

Here is another example, where i.e. is interchangeable with 'that is'

Some poems are mnemonics, i.e. they are designed to help you remember something.

With the same meaning, 'in other words' always be written like this when introduce a clause:

  1. They signify, in other words, that everything is gift.

  2. He was economical with the truth in other words, he lied.

So, put simply, is 'that is' or 'i.e.' a kind of conjunction or punctuation that can lead independent clauses?

  • In your example, that is introduces a clause, not a sentence. In everyday speech, it might sound more like a new sentence if the speaker took a few moments to remember that the trains might not be running. Sep 7, 2023 at 9:54
  • @Kate Bunting ,thanks,i have edited it.
    – Mr. Wang
    Sep 7, 2023 at 10:04
  • I'd put at least a dash (more likely a full stop) after the preceding assertion which is being "expanded / restated" after that is. A comma seems inadequate, to me. Sep 7, 2023 at 10:21
  • @FumbleFingers Are both dashes and parentheses ok?
    – Mr. Wang
    Sep 7, 2023 at 10:23
  • Parentheses are an orthographic device to help the reader identify the contents as "peripheral" to the containing utterance, but probably the main reason for using them is brevity. So your example would be a bit "unbalanced" if you just used parentheses instead of a dash or period. The "short and to the point" spoken version would more likely be I'll meet you in the city if the trains are running, where you probably wouldn't pointlessly enclose the caveat in parentheses. It partly depends whether you'd pause after the word city there. Sep 7, 2023 at 10:46

1 Answer 1


I'll meet you in the city, [that is, I will if the trains are running].

Some poems are mnemonics, [i.e. they are designed to help you remember something].

They signify, [in other words, that everything is gift].

He was economical with the truth – [in other words, he lied].

No, they are not conjunctions.

The bracketed expressions are supplements, loosely attached expressions set off by intonation and punctuation presenting supplementary, non-integrated content. They are non-dependency constructions.

Often, supplements contain indicators which serve to clarify the nature of their semantic relation to their 'anchor', i.e. to the expressions they relate to.

Indicators consist of expressions like "that is", "namely", "in other words", "i.e", "viz" etc.

Note that indicators are part of the supplements that contains them, as the brackets indicate.

  • 1
    "They signify, in other words, that everything is gift." is a bit different from the other examples. Here "in other words" is superfluous and supplemental (and could be moved to the start or end), but "they signify" on its own doesn't have the same meaning: "They signify that everything is gift" would be the reduced version.
    – Stuart F
    Sep 7, 2023 at 12:50
  • We can't say that because we don't have the full text, so we don't know the antecedent of "they".
    – BillJ
    Sep 7, 2023 at 13:15

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