a. for what reason, purpose, or cause?: why are you here?. b. (used in indirect questions): tell me why you're here. /waɪ/ IPA guide Other forms: whys Definitions of why noun the cause or intention underlying an action or situation, especially in the phrase `the whys and wherefores' synonyms: wherefore The meaning of WHY is for what cause, reason, or purpose. How to use why in a sentence. Learn the correct use of 'why do' vs 'why doing' with this clear, concise guide. WHY definition: for what? for what reason, cause, or purpose?. See examples of why used in a sentence. WHY definition: 1. for what reason: 2. used to express surprise or anger: 3. the reasons for something. Learn more. The word why is essential for seeking understanding, clarifying reasons, and expressing curiosity or surprise. Its applications span everyday conversation, academic exploration, and storytelling. Why do is used with plural subjects, while why does is used with singular subjects. Therefore, the choice between the two depends on the subject of the sentence. Easy Learning Spanish Grammar. When we ask for reasons in speaking, we can use the phrase why is that? In informal conversations we often say why’s that?: ….