1An interjection expressing denial, disagreement, surprise, or hesitation. Extremely common at the start of spoken sentences — depending on context it can mean a flat 'no', or function more like 'well...' or 'oh'.
いや、今日は行けないよ。
No, I can't go today.
いや、それは違うと思う。
No, I don't think that's right.
いや〜、疲れた一日だった。
Man, what a tiring day.
いや、待って、もう一回考えさせて。
Wait, hold on, let me think about this again.