Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
considerable (adv., adj., n.)
All adjectival uses of considerable are Standard: Considerable [or a considerable] rain fell during the night. The flat adverb considerable still exists but seems to be limited to Common and Vulgar English today; most Standard English insists on considerably as the adverb: She felt considerably [not considerable] better this morning. Most uses of considerable as a noun are Conversational or Informal; editors would almost certainly change considerable to an adjective rather than a noun in each of these uses: The fans raised considerable of an outcry [a considerable outcry] over the decision. He’s written considerable [a considerable amount] about his family.
