It is a serious, and sometimes fatal, disease that may become epidemic in crowded, unsanitary living conditions.

I'm trying to find the name of grammar structure (a very technological term, not just something like "parenthetical phrase to add additional information", as I seek to find every information about it) of "and sometimes fatal", a parenthetical phrase and what seems to be a coordinative adjective.

I just do not understand how it is grammatical to wrap that conjunction and adjective in commas like that. Isn't comma supposed to come before the conjunction only when a new independent clause is beginning?

  • It is perfectly legitimate to use commas around a parenthetical phrase, and the phrase in question is, regardless of the other roles it may fill and characterizations it may carry, a parenthetical.
    – Hot Licks
    Jan 13, 2016 at 2:15
  • It should be noted that some authors would omit the commas. There are differing opinions on the use of commas in such situations, and there is also a slightly different "shade" of meaning conveyed by the presence or absence of the commas.
    – Hot Licks
    Jan 13, 2016 at 4:47

3 Answers 3


It is called a "parenthetical phrase." While you state that is not the name you are looking for, that is the grammatical term for it. More specifically, and within the subset of parenthetical phrases, it is called an "aside." Basically, you are more right than you imagined, more on the right path than you seem to have thought.

  • That website said that aside conveys an apologetic attitude. Jan 13, 2016 at 22:37
  • It says "often," not "always," not even "mostly." ("...often denoting an ingratiating or apologetic attitude) These are not definitive of an aside, just a common examples of one. Jan 14, 2016 at 8:06

Would you be happy with: '... a serious (and sometimes fatal) disease ...'? The comma is actually a tiny parenthesis. Since they are represented in speech by a pause, '(' and ')' sound the same (and aren't apparent at the beginning or end of a sentence).

  • Hm. But what licences the use of commas, and, in your case, parenthesis? According to you, it is just supposed to be the representation of the pause in a speech, and those, in many occasions, are considered ungrammatical in written texts. So I do not know if it is grammatical or not. Jan 13, 2016 at 0:41
  • @cityofunited - You misunderstand what "written texts" means.
    – Hot Licks
    Jan 13, 2016 at 2:16
  • @HotLicks ????? Jan 13, 2016 at 22:36
  • @cityofunited - All writing (outside of things like tables and bulleted lists) is effectively transcribed speech. The semantically significant pauses and tone patterns of speech are represented (somewhat poorly) in written text using punctuation. What is grammatical in speech is grammatical in written text.
    – Hot Licks
    Jan 13, 2016 at 22:46
  • Oh... I was referring to pauses made not based on a written speech accidentally or intentionally. But thanks for the input. Jan 13, 2016 at 23:05

On the grammatical level, you could call it a "coordinate/adjective-modifying adjectival phrase," and on the functional level, you could say that it places scalar focus on the head adjective.

  • Why is the phrase after and set off with and? Jan 13, 2016 at 0:55
  • Also, there is NO technical term for it, right? Jan 13, 2016 at 1:01
  • @cityofunited most words in English can be coordinated with "and". English is said to be "head-initial," meaning that the modifying portion of a phrase tends to come after. I have provided you with a technical term. you can probably find others in the literature. consider reading further in Huddleston&Pullum
    – user31341
    Jan 13, 2016 at 1:44

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