I was reading an article on ScienceDaily and came across the following:

The team is now trying to understand what happens to these cells in other autoimmune diseases to evaluate their potential not only for diagnostic but also to identify which patients may benefit with medicines that interfere with the production of harmful antibodies.

I looked up this word in some dictionaries, and according to them it's often used in the plural when it means "the practice of diagnosis" — which I think is the case. But why is it in the singular here? Is the meaning of this word different in some way when it's used without the "s"?

I believe it's not a typo, because I think I've seen other words used in such a way somewhere.

2 Answers 2


Honestly, I think the example paragraph is wrong.

First, it is true that it is becoming common to use "diagnostics" as a plural. However, "diagnostic" is not traditionally a noun. It's an adjective. You can have a diagnostic procedure or a diagnostic tool and you can have diagnostic procedures and diagnostic tools. However, as our world becomes more technical in nature, it's becoming more common to drop the actual noun and use "diagnostic" as a general term.

Nevertheless, how the word is used in that paragraph is simply incorrect. It should have said...

...to evaluate their potential not only for diagnostic purposes, but also to identify...

Regrettably, journalists are often under tight deadlines and regularly make mistakes.

  • Or, perhaps just "for diagnostics" or "for diagnosis" would be ok.
    – BobRodes
    Commented Aug 12, 2017 at 22:27

I second JBH's answer. I think it is indeed a typo. Diagnostic is an adjective; diagnostics and diagnosis are nouns. As you have found for yourself, the two nouns have a slightly different meaning, and either meaning appears to work well in the context of the sentence. I would lean towards diagnostics myself, though.

So it would seem that your intuition is basically accurate. However, diagnostics is not the plural of diagnostic; it is simply a different word, analogous to economics and economic. Incidentally, economy is also analogous to diagnosis in its relationship to the other two words.

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