Sometimes we have two things so closely associated in use that they may be considered as forming a single idea, so that we may use the article before the first one only. For example:

INTERROGATIVE ADJECTIVES

255. You remember we found in the study of pronouns that we have interrogative pronouns which we use in asking questions when we do not know the name of the object concerning which we are asking. We also have adjectives which we use in asking questions when we do not know the number or quality of the object concerning which we are asking. For example:

Which and what are the interrogative adjectives in these sentences.

Interrogative adjectives are adjectives used in asking questions.

INDEFINITES

256. We have one more class of adjectives called indefinites.