A casual interjection used to express refusal, denial, or disagreement. Often used in informal conversation.
"Have you eaten yet?" "No, not yet."
No, I think that's wrong.
いや is a casual, informal way to say no, while いいえ is the polite, formal counterpart used with strangers or superiors.
Usually written in kana; the kanji form 否 is rare and literary.
Kanji form is uncommon in modern usage; mainly seen in formal or literary contexts.
The exact derivation is uncertain; it is a native Japanese interjection expressing negation or refusal.