I'm having trouble with was vs. were in the following sentences:
1. Fuel-stained soil and street waste was discovered south of the site. 2. During the building excavation, 50 tons of soil were removed from the property.
The subject in the 1st sentence is "Fuel-stained soil and street waste," with two mass nouns (soil, waste) thus the singular verb "was" is called for, correct? The subject in the 2nd sentence is "50 tons of soil," which is plural (tons of soil), thus the plural verb "were" is called for, correct?
The first sentence is slightly tricky. Although both the nouns in the subject are mass nouns, they are still two different nouns. So technically, the verb should be plural. Take for instance a sentence like "Water and alcohol are common solvents used in cosmetics." The subject has two mass nouns that are treated as distinct. However, sometimes such subjects are considered as a single unit rather than as having distinct entities. In such cases, it may be acceptable to use a singular verb, for example, "Bread and butter is her favorite breakfast." If you think of "fuel-stained soil and street waste" as one whole entity, then the use of the singular verb is fine.
According to most widely used scientific style guides, units of measurement should be treated as collective singular nouns. Thus, in the second sentence, the verb should be singular even if the noun "tons" is plural. So whether you say "15 mL" or "fifteen milliliters," the verb should always be "was."
[Mriganka Awati is Senior Editor - Quality and Training, at Editage.]
It is natural to associate numbers with the plural form. When talking about more than one of something – days, samples, experiments, etc. – we tend to use the plural form of the verb, as in "the days were short," "the samples were dried," or "the experiments were repeated."
The expression "a number of" also belongs to the same category—it is always followed by the plural form, as in "a number of days passed" or "a number of people were present." Do not be misled by the indefinite article a in that expression: the expression is always used to indicate more than one of something and therefore takes a plural noun and a plural verb.
On the other hand, the expression "the number of" is different and always takes a plural noun followed by a singular verb because the expression is used to refer to the exact number that makes up a collection or a group. The expression emphasizes a precise quantity and is used when the exact number is more important than just the fact that there were many, as in "The number of plants in each plot was 25" or "The number of participants was greater in summer than in winter."
[This is part of the series, Nuances of English, that contain posts and hints that cover the teeny-weeny trivialities of the English language that, at last count, numbered quite a lot.]