English interrogative words

The English interrogative words (also known as "wh words" or "wh forms") are words in English with a central role in forming interrogative phrases and clauses and in asking questions. The main members associated with open-ended questions are how, what, when, where, which, who, whom, whose, and why, all of which also have -ever and -soever forms (e.g., whatsoever). Those associated with closed-ended questions are whether and if.

The main role of these words is to mark a clause as interrogative. For example, How did you do it? is marked as an interrogative clause by the presence of how, and in I wonder whether it's true, whether marks the subordinate clause whether it's true as interrogative.

Extended membership

Along with the words listed above, the members include some older or archaic words, including whence, whither, and other compound prepositions such as whereby, wherein, formed with one of the central interrogative words + a preposition.

Semantics

When used in a main clause, the interrogative words do no refer but rather question. For example, who in Who likes sewage? does not pick out a specific individual in the world, but rather asks about the identity of such an individual, should they exist. In a subordinate clause, though, this may be different. For example, how in I know how to do it, denotes a particular way of doing it rather than asking about a way.

Lexical categories and syntactic functions

Although the main role of interrogative words is to mark a clause as interrogative, each also has a syntactic function when used in a phrase, just as any word would. For example, in What time works?, what functions as a determiner, while in Who arrived?, who functions as the subject.

Different words have different functions depending on their lexical category. For example, while a pronoun like who may typically function as a subject, a preposition like when rarely does so. Moreover, the form of the word may constrain its function. Whose, the genitive form of who, for instance can function as a determiner, while who cannot.

Interrogative vs relative words

There is significant overlap between the relative words and the interrogative words, but the relative word while is not an interrogative word, and, in Standard English, what and how are mostly excluded from the relative words. Most or all of the archaic interrogative words are also relative words.

As an interrogative word, whose is perfectly limited to denoting persons, while relative whose may denote non persons, as in a book whose cover is missing.