Say you have in front of you three marbles, one of which is red, another blue, and the last one yellow. Is the sentence "A third of these marbles is blue." grammatically correct?


The reason I chose this particular setup is because 3/3=1. So "a third" represents a single object. If I said "half of the strips of the US banner are white", "half" represents 25 objects, so it seems natural to use the plural "are". But if the fraction only covers one object, the justification for using a plural becomes less clear.

  • 1
    Could you please say why you would rather say this than (say) just "One of these marbles is blue."? That would be the natural thing to express it.
    – Tuffy
    Jan 22, 2022 at 17:34
  • I have added a justification in an edit to my question.
    – kiyopi
    Jan 22, 2022 at 21:10
  • I guess the synesys phenomenon mentionned in the question linked by Edwin answers my question. Thank you.
    – kiyopi
    Jan 22, 2022 at 21:13

1 Answer 1


Only "one" takes singular agreement. Every other quantity takes plural agreement - including fractional quantities. But there's a catch.

In your example, you need "is/are" to agree numerically with "these marbles", not "a third".

From the University of Toronto's website:

With fractions, percentages and indefinite quantifiers (e.g., all, few, many, much, some), the verb agrees with the preceding noun or clause:

  • One-third of this article is taken up with statistical analysis.
  • One-third of the students have graduate degrees.

Not the answer you're looking for? Browse other questions tagged or ask your own question.