grammar - Question about singular/plural with present perfect

Is the following sentence correct?

"Two thirds of land has already been sold."

Is it correct as it has the singular have verb "has" or it shoulb be rewritten with the plural verb "have"?

Answer

In the question and related comments, two separate "fraction" issues have emerged.

1. Should the verb be plural because it refers to a fraction?

Generally speaking - though there are exceptions - the fraction takes the same plurality as the thing it modifies; see here for a good explanation. In the specific context of the present question, "the land" is singular therefore it's appropriate to use the singular verb "has".

2. Should the fraction be hyphenated?

This depends on how the fraction is being used. In situations where the fraction is a noun, there should be no hyphen, whereas if the fraction is being used as an adjective to describe something else, it should be hyphenated; see here for an explanation. For example:

• "Two thirds of the land" [the "thirds" here is a plural noun, with
  "two" being the adjective that modifies it];


• "Two-thirds share of the land" ["thirds" is now acting as an
  adjective modifying the noun "share", and "two" is acting like an
  adverb modifying "thirds"].

So in the present question, it's correct to write the fraction without the hyphen.