When I'am writing a paper, I did not know what is the difference between "is" and "are"?

Should I write:

"DNA is a part of....."

instead of:

"DNA are a part of....."?

I think that plurals can use with "is" or "are", but when I googled and googled, it can only use "is" with singles, and can only use "are" with plurals.

  • Why do you think DNA is plural? Commented May 13, 2018 at 16:24
  • Because there are many dnas.
    – user298438
    Commented May 13, 2018 at 16:26
  • Are you sure about that? Deoxyribonucleic acid (DNA) is a thread-like chain of nucleotides carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses. Wikipedia Commented May 13, 2018 at 16:28
  • Thanks, I'am mistakenly think dnas are plural. I will edit it.
    – user298438
    Commented May 13, 2018 at 16:31
  • The critical question is whether DNA is a "countable noun". Any noun that is non-countable e.g. water, air, sand etc is treated as singular. Hence, unless, you are speaking about several different types of DNA - my suggestion is that it takes a singular verb.
    – WS2
    Commented May 13, 2018 at 18:18

1 Answer 1


Well, the main difference between “is” and “are” is that “is” is singular while “are” is plural. This means a singular subject would be paired with the singular verb “is.” As an example,

The man is a member of the circus performing tonight.

Additionally, “are” is plural, so it must be paired with a plural subject. As an example,

The sailors are currently hungry since they are running out of food.

Because of this, you would use “are” in your provided sentence because “DNAs” is plural. However, DNA is usually not mentioned in the plural form unless you are talking about multiple different types of DNAs in multiple different beings. Example: https://www.ncbi.nlm.nih.gov/pubmed/17125740

Note: If you ever decide to change the subject of your sentence to simply “DNA,” then use “is” instead of “are.”

  • Water is a component of every human body. Would you use 'waters' when describing the water in a number of individuals, even considering that the composition (the deuterium content) is different in every case ?
    – Nigel J
    Commented May 13, 2018 at 16:34
  • @NigelJ I have no idea why the OP used DNAs in his sentence, but I took a look at the .gov article I provided, and I realized that they used “DNAs” when talking about crossing DNA from different human bodies. However, I certainly agree with you in that “DNAs” is likely not the correct usage here. Commented May 13, 2018 at 16:37
  • 1
    Yes, agreed. In that case they use the expression 'multiple DNAs' which I agree makes sense in that particular context.
    – Nigel J
    Commented May 13, 2018 at 16:52
  • 1
    DNA is not plural. Any chemists would never say "DNAs". I understand.
    – user298438
    Commented May 31, 2018 at 17:36

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