why
(noun, adverb, interjection)
adverb
1. For what cause, reason, or purpose.
2. Introducing a complete question.
- Why is the sky blue?
- Why did you do that?
- I don’t know why he did that
3. Introducing a verb phrase (bare infinitive clause).
- Why spend money on something you already get for free?
- Why not tell him how you feel?
4. Introducing a noun or other phrase.
- Why him? Why not someone taller?
interjection
1. An exclamation used to express indignation, mild surprise, or impatience. "Well, I'll tell you...".