Before a vaccine was finally discovered by an American scientist Jonas Salk in 1955, more than 80% of polio patients received help from the foundation.

I was given options of a) keeping the bold part as it is or b) changing it to "scientist, Jonas Salk,". I had chosen a) without hesitation, but apparently, b) is correct. However, I don't understand why because isn't Jonas Salk an essential information here?


To be clear, the original version is wrong.

The use of a pair of commas would make it nonessential information and work with the indefinite article.

To demonstrate:

 . . . by an American scientist, Jonas Salk, in 1955 . . .
 . . . by an American scientist in 1955 . . .

The name adds information to the sentence, but it is not a requirement to the sentence structure.

To make it essential information, there should be no commas but there should also be no indefinite article (either the definite article or no article at all):

. . . by the American scientist Jonas Salk in 1955 . . .
. . . by American scientist Jonas Salk in 1955 . . .

Essential information, in this sense, is a grammatical phrase. If you think that the name of the scientist is essential to the meaning you want to convey, then you should not be putting the name inside a pair of parenthetical commas. (However, in this case, that wasn't one of the possible answers.)


In your example, yes, "Jonas Salk" is essential information, but it's a modifier of "*American scientist", so

by an American scientist, Jonas Salk, in 1955,

BTW, since a specific American scientist is being spoken about, it might be better as

by the American scientist Jonas Salk in 1955,

You can also think of it this way

by Jonas Salk, an American scientist, in 1955,

  • "the American scientist, Jonas Salk, in 1995" would be incorrect, because it sounds like Jonas Salk is the one and only American scientist. In this case it's a nonrestrictive clause and you'd drop the commas. – mamster Sep 30 '18 at 16:11
  • @mamster If one says "David Cameron, the former UK Prime Minister" it does not mean he is the one and only former UK Prime Minister. – Peter Sep 30 '18 at 16:19
  • 1
    You've reversed the order of the clauses. In this case, "the former UK Prime Minister" is the non-restrictive clause. It distinguishes him from "David Cameron, the gas station attendant," and so on. – mamster Sep 30 '18 at 16:20
  • Also, the use of the definite article complicates things a lot. "The American scientist" is very different from "American scientist" or "An American scientist" with regards to how the following clause should be punctuated. – mamster Sep 30 '18 at 16:22
  • Oh, and "The American scientist, Jonas Salk, ..." could be fine if you had been talking about two scientists, an American and a Tanzanian, and wanted to focus on the American one. – mamster Sep 30 '18 at 16:23

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