Why is 'herd of cows is' proper and not 'herd of cows are'?
When referring to a herd of cows, the to-be verb "is" is proper. This is because the "is" is referring to the word "herd", not "cows", and since herd is singular, the to-be verb is also singular.In contrast, if it were "herds of cows", then "are" would be proper because herds is now plural, so the to-be verb also becomes plural.