Is it grammatically correct to omit the second "the" in the sentence

The viscosity and the density of water characterize its speed.

and write instead

The viscosity and density of water characterize its speed?

  • 3
    Much of the time you can get away without using the second article. But occasionally, in order to emphasise that there are two different things involved, it helps to repeat the aticle. Or you might feel inclined to Both the viscosity and density of water...
    – WS2
    Feb 5, 2015 at 9:58
  • 3
    The Good, The Bad and The Ugly, on a lighter vein :) There is a genuine issue of missing the intent. The 'viscosity and density' could imply these factors have to be seen together to characterize the speed. 'The viscosity' and 'the density' could imply that each of them could individually impact the speed. Feb 5, 2015 at 10:11
  • Grammatically correct but ambiguous in meaning, as pointed out. Also extremely common.
    – Pete W
    Apr 29, 2021 at 17:06

2 Answers 2


Repeating the article can avoid ambiguity when adjectives get involved. "The black dog and cat" might mean "The black dog and the black cat" or "The black dog and the cat [of any colour]." "The black dog and the cat" clearly associates "black" only with the dog.


No, not really. In your example, "the viscosity and density of water" is perfectly okay, and it means the same as "the viscosity of water and the density of water", but a "the" has not been omitted, nor has "of water" been omitted. Instead, a conjoined noun, "viscosity and density", has been used as the head noun of the noun phrase. There is only one noun phrase there, consequently, there is only one "the". But "[[the viscosity of water] and [the density of water]]" has two noun phrases, and consequently there are two "the"s -- one for each noun phrase.

Words that are not present aren't necessarily "omitted".

If you want to test whether there are actually two noun phrases present, perhaps you could tell by trying to associate different nonrestrictive relative clauses with each noun phrase.

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