This question is best explained by an example. Ignore the mathematical context, it doesn't really matter.

... as x tends to 0, the point P slides towards P', so cos x (and hence 1/cos x) both have a limit equal to 1. ...

Given that parentheses are usually meant as an aside, if I read the text ignoring the parentheses:

... so cos x both have a limit equal to 1 ...

the "both" here is grammatically incorrect (as, of course, cos(x) is a single "thing").

So here comes the question in the title: Do sentences need to remain grammatically correct if text in parentheses are ignored? And as a side question, what would be a better thing to use in the example?

  • The mistake is you should set off and hence 1/cos x with commas, not brackets. If not, you'd have to discard both and continue with ...has a limit. – FumbleFingers Mar 29 '16 at 15:10
  • @FumbleFingers I've modified my answer according to your comment. – Cyberherbalist Mar 29 '16 at 16:45
  • More generally, as for many other grammatical terms, there is no agreed definition of 'parenthetical'. In Parentheticals in Spoken English: The Syntax-Prosody Relation by Nicole Dehé is found ... – Edwin Ashworth Mar 29 '16 at 23:53
  • Elements which have been considered parentheticals in previous literature form a heterogeneous set and there is no general agreement as to the exact definition of a potential class of parentheticals…. Syntactic amalgamation has been analysed in terms of parenthesis: … (1.19) Syntactic amalgamation: (a) John invited you’ll never guess how many people to his party. (Lakoff 1974: 321) / (b) John is going to I think it’s Chicago on Sunday. (Lakoff 1974: 324) >> [the claimed parentheticals in italics]. Obviously, omitting these destroys grammaticality. – Edwin Ashworth Mar 29 '16 at 23:55

Wikipedia states: "Parentheses (singular, parenthesis) (also called simply brackets, or round brackets, curved brackets, oval brackets, or, colloquially, parens) contain material that serves to clarify, or is aside from the main point."

This suggests that the sentence should be read as if the text in parentheses were not there, and as you indicate, "both" is grammatically incorrect in this particular case.

Since the information in parentheses seems to be more than a mere aside, I would have written it differently, removing the parentheses:

so cos x, and hence 1/cos x, both have a limit equal to 1

although a better formulation (less awkward) would be

so both cos x, and hence 1/cos x, have a limit equal to 1

But that's my take. Others may differ.

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  • Yeah - I think the bottom line is sentences do need to remain grammatically correct if text (and enclosing parentheses) are ignored, so technically speaking this sentence is "invalid" with those brackets. – FumbleFingers Mar 29 '16 at 16:59
  • Whilst the conclusion may not be incorrect, arguing that a semantic property should logically control a syntactic practice is often unsafe. – Edwin Ashworth Mar 29 '16 at 17:09
  • I agree with @FumbleFingers, especially since I don't believe parenthetical text should be ignored. I've seen it done in verbal readings of text, and in my opinion doing that detracts from the meaning of the text. – Cyberherbalist Mar 29 '16 at 18:07
  • @EdwinAshworth I am impressed with your sentence, but for some reason it doesn't cause any meaning in my brain. I guess it's a linguistically sophisticated sentence. Where can I read more about the concept? – Cyberherbalist Mar 29 '16 at 18:09
  • Essentially, I'm saying that 'sentences need to remain grammatically correct if text in parentheses is ignored' needs to be quoted from some recognised authority in an 'answer', rather than 'The Wikipedia statement ... suggests that sentences need to remain grammatically correct if text in parentheses is ignored'. Paraphrases, for example, do not need to use the same grammar. – Edwin Ashworth Mar 29 '16 at 21:38

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