Is two-thirds plural?

Is 2/3 always, sometimes or never plural?

E.g.

1a) 2/3 of the pizza were eaten.
1b) 2/3 of the pizza was eaten.

2a) 2/3 of the visitors were men.
2b) 2/3 of the visitors was men.

I feel that example 1 could go either way but example 2b sounds very wrong.

Is there a rule for this?

• – user10893
Commented Sep 19, 2011 at 6:09

It depends on whether two-thirds (or any similar proportion) is regarded as a measure of amount or of number. In (1), the emphasis is likely to be on the amount of pizza eaten, and not on the number of individual thirds, so (b) would be appropriate. In contrast, in (2) the emphasis is on the number of visitors who were men, so plural concord, as in (a), is required.

• +1 concise answer. I was guessing it had something to do with amount and number.
– paul
Commented Sep 19, 2011 at 7:26
• But then, it would be correct to say 2/3 of the pizza were eaten if I wanted to express how many thirds have been eaten (ie, number of thirds eaten)? Commented Sep 19, 2011 at 10:11
• Saying "Two thirds of the pizza were eaten" sounds funny to me, but you could certainly say "Two fifths of the whiskey were drunk." Commented Sep 19, 2011 at 12:57
• "Fifth" is not 1/5 in that case, so "two fifths of the whiskey were drunk" isn't a good construction. I'd say "two-fifths of the whiskey was drunk" or "two fifths of whiskey were drunk", with the second one equivalent to "two containers of whiskey were drunk". Commented Sep 19, 2011 at 17:38
• @jprete: If you can say "Two bottles of the whiskey were drunk" (I certainly think you can), why not "Two fifths of the whiskey were drunk"? It does mean something slightly different than "Two bottles of whiskey were drunk." Commented Sep 19, 2011 at 17:59

Yes and no. Yes, when you're talking about multiples of fractions eg. two thirds they are plural. But when you're talking about a portion of a single item, that item is singular.

1). One third of the pizza was eaten. (part of one pizza was eaten)

Two thirds of the pizza was eaten. (part of one pizza was eaten)

The subject is pizza - singular. If you have one third of a pizza, and I have one third of that same pizza we have two thirds (plural) of one pizza (singular).

Of course this changes when the subject becomes plural:

One third of two pizzas were eaten. (part of two pizzas were eaten)

2). One third of the visitors were men. (multiple visitors were men)

Two thirds of the visitors were men. (multiple visitors were men)

The subject in this case - men - is plural.

The sentence doesn't make sense if the subject is singular (Two thirds of the visitors were man). I'll just change the meaning slightly so it works:

One third of the man was on fire. - Singular Two thirds of the man was on fire. - Still singular

Clear as mud.

• Does this still hold if we are talking about one third of the visitors and there were three visitors? (Meaning we are talking about one visitor.)
– user
Commented Sep 19, 2011 at 9:55
• @Michael: it does not matter if you are talking about one third of three visitors or one third of six visitors. It's still plural. Commented Sep 19, 2011 at 12:53
• @Michael: Yes. The assumption in this kind of sentence is that you don't know the number, or at least that the number is unspecified. That is, in real-life usage you would write something like, "We counted visitors as they entered, and one-third of them were men." I suppose you might write something like, "There were three visitors, and one-third of them were men." But grammar rules are not based on the details of a specific example like that, but on general principles. Largely this is because it would often be impossible to know things like the actual number in advance.
– Jay
Commented Sep 19, 2011 at 14:32
• Like suppose you put up a sign at the entrance to whatever that said, "All visitors must wear shoes." Only one visitor comes today. Does that mean that the sign should be changed to "All visitor must wear shoes"? But how could you know in advance? Grammar is tough enough without having to alter it for that sort of detail.
– Jay
Commented Sep 19, 2011 at 14:32
• @PeterShor is right. The subject is "visitors". "One third" is an adjective. Commented Sep 20, 2011 at 0:49

It depends on what the fraction is of. If you are referring to two-thirds of an uncountable noun ("two thirds of love is understanding") then any further reference to the "two thirds" should be singular. If you are referring to two thirds of some finite (countable) quantity, such as "two-thirds of people in the U.S. are brunettes", then that "two-thirds" reference should be plural.

• I would posit that while "two thirds of" a singular or collective noun would be singular. [Hypothetical examples--not real stats] Two thirds of the pizza made by fast food chains in the U.S. contains real mozzarella cheese; two thirds of the pizzas ordered in the U.S. are delivered to college dormitories. Commented Jan 19, 2015 at 20:57
• @supercat: I'd write your first statement thus, "two thirds of the pizzas made by fast food chains in the U.S. contain real mozzarella cheese," and consider your example either to be erroneous or to mean that every pizza made by every fast food chain in the U.S. contains 2/3rds mozzarella and 1/3rd some other ingredient. Commented Aug 10, 2018 at 11:55
• Saying "2/3 of the pizzas" would mean the fraction was measuring by count, while "2/3 of the pizza" would mean 2/3 of the pizza by some other metric (typically mass). For example, if a company sells 20 jumbo 1kg pizzas that don't mozzarella and 80 mini 250g pizzas that don't, then only 20% of the pizzas would contain mozzarella but 50% of the pizza (collective) would contain mozzarella (20kg of jumpo pizza with mozzarella and 20kg of mini pizzas without), Commented Aug 10, 2018 at 14:00