Interrogative Determiners
Use the term for a question word functioning as the determiner of a following noun phrase. “Which” typically asks within a restricted set, “what” is often more open-ended, and “whose” asks about possession. When the word stands alone instead of modifying a noun, it is functioning differently.
Interrogative determiners are question words such as “what,” “which,” and “whose” when they come before a noun and help specify what is being asked about: “Which route?”, “What time?”, “Whose bag?” The same words can have other grammatical roles, so identify the noun-modifying function in context.
Key details
Important caveats
Boundary
Do not label every occurrence of what, which, or whose an interrogative determiner. In “Which do you prefer?”, “which” stands without a following noun and functions as an interrogative pronoun.
Further guidance
Choice
Use “which” when the expected possibilities are restricted or identifiable; use “what” more naturally for a broader open set. “Whose” asks about possession.
Diagnostic
Check whether the question word directly introduces or determines a following noun: “which option,” “what reason,” “whose notes.”
Worked Example
“Which train leaves first?” contains the interrogative determiner “which” modifying “train.” “Which leaves first?” asks a similar question, but “which” now stands alone.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Noun phrases: dependent words (opens in a new tab)Cambridge University Press · Places which, what and whose among interrogative words that function as determiners before noun heads.
- Which (opens in a new tab)Cambridge University Press · Distinguishes which as a determiner when it modifies a noun in questions from its use as an interrogative pronoun and explains which-versus-what choice.