noun
terrible twos; phase of toddler defiance
Colloquial term for the developmental stage around age two when toddlers frequently say いや (no) and resist parental instructions. Used mainly in parenting and childcare contexts.
うちの子もイヤイヤ期に入って、何でも「いや」と言うようになった。
Our child has also entered the terrible twos and now says 'no' to everything.
イヤイヤ期の対
Many parents struggle with how to handle the terrible twos.
反抗期 refers to a broader rebellious phase, often in adolescence, while イヤイヤ期 specifically describes toddler defiance around age two.
From いやいや (toddler's repeated 'no') + 期 (period). A modern colloquial coinage.