When writing about specific quantities, should the verb reflect a singular or a plural value? Do abbreviations vs. spelled-out words make any difference?

I took 2 ml of water, which was/were then added...

Six microliters of protein solution was/were placed in a centrifuge...

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    Related: Are units in English singular or plural? – Dusty Sep 8 '11 at 19:04
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    I think most native speakers would accept either, but I've found the scientific community tends to use the singular in instances where the quantity represents one "object". (i.e. 6 ml in one container as opposed to 1 ml each in 6 containers) – tdhsmith Sep 9 '11 at 3:28
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    This is not a duplicate question, despite being related. The other question asks: is it 2 milliliter or 2 milliliters of water? This one asks: does the 2 ml. water take a singular or plural verb? – Peter Shor Sep 9 '11 at 4:09

These constructions are called "mass nouns" (or something comparable). Although they refer to more than one thing (e.g., more than one milliliter of water), they treat these things as a single unit.

Mass nouns take singular verbs - not plural (reference and reference).

Take your first example:

I took 2 ml of water, which was/were then added...

The water, despite being more than one milliliter, was added at the same time, as a single unit. It would not be helpful (semantically or grammatically) to think of each milliliter of water as being added separately. Instead, treat the mass noun as the group it is, and use the singular.

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    I agree with the reasoning that units of measure generally comprise a single amount/entity and can be grammatically singular (though there may be reasons to keep them plural as well). But are you calling the units mass nouns or the substances? I would call units count nouns if anything; their primary purpose is for counting. – tdhsmith Sep 9 '11 at 3:22
  • If you have issues with another answer, you should put a comment about it there, not in your answer. Your answer should stand alone and not reference others. – D Krueger Sep 9 '11 at 3:23
  • @lettuce_pants: I didn't mean to distinguish between the units and the substances. Together, I think, they constitute a mass noun. @D Krueger: Duly noted, and thanks. Updated to reflect your advice. – ect Sep 9 '11 at 3:47
  • Do I still use a singular verb if cup is not used as the unit of capacity but literally as a cup? E.g. 5 cups of water was/were poured into the container? – clickbait Jun 22 '18 at 6:05

Use singular verbs with units. This usage is so because the measurement results in a quantity of a substance, e.g., 2 litres (better written as 2 L) is a quantity of water with the water still being a non-count noun. To avoid this problem, use the measured quantity as the object of verb as illustrated below:

a. Add 2 L of water and stir. b. Tie 10 m of the rope around the neck of the animal and tether it.

Never write the word name of a unit of measure after a number to represent the result of measurement, e.g., 5 metres is incorrect. Wrte 5 m. However, when used as an adjective, both the symbol and word name are correct, e.g., 5 km journey and 5-kilometre journey. Do not insert a hyphen when the unit symbol is used.


Like other nouns, if the number is exactly 1, then the unit should be singular. Otherwise, it will be plural.

So in your examples, were is correct.

However in the following case

1L of solvent was utilized.

was is correct since it's a single liter.

  • Would you say two minutes are not a long wait for a dentist's office? I don't think so. – phoog Dec 21 '15 at 22:25
  • 'Fifty dollars for a ticket are a bit stiff'? – Edwin Ashworth Sep 8 '19 at 12:04

Whether count (mass) nouns take singular or plural noun differs in both context and whether it’s e.g. British or American English. Brits like to think of most count nouns as plural entities and would therefore say:

The staff have been very productive this month.

In contrast, Americans prefer:

The staff has been very productive this month.

However, in this instance, scientific style becomes the key. In scientific texts, ‘amounts’ are taken to be singular count nouns, even in the UK. For example:

50 litres/liters is a lot of water.


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