Question words, interrogative words, WH question words, wh-words, interrogative pronouns (all of these mean the same)

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What: Question Words, wh-questions Why: Question words, wh-questions When: Question words, wh-questions Where … ? vs Where … at? Question words, wh-questions Who: Question words: subject/object question, whom Which: Question words: Which of / who of How: Question words: How old/fast/long/many/much Why vs what for? Question words For what reason vs for what purpose: Question Words