also: いえ
interjection
Polite negative answer to a yes/no question or statement. In casual speech, ううん or いや are more common.
「コーヒーはいかがですか？」「いいえ、結構です。」
"Would you like some coffee?" "No, thank you."
interjection
Used to modestly deflect thanks, similar to 'it was nothing'. Often repeated: いいえ、いいえ.
「手伝ってくれてありがとう。」「いいえ、どういたしまして。」
"Thank you for helping me." "You're welcome; it was no trouble at all."