Normally, the indefinite article combines with singular countable nouns. However, we often find linguistic expressions in which an indefinite article combines with plural countable nouns, as in a good many books, and with uncountable nouns, as in a good knowledge of Greek. In the former case, the combination of a and the plural noun books looks unnatural at first glance. In the latter case of a good knowledge as well, the noun has been traditionally treated as partly countable or as an exception in that knowledge accepts the indefinite article while it is not allowed to become a plural. This research discusses the way such unique combinations have been made possible.