Having many interrelated parts or aspects; not simple — complicated or intricate. Also used for mixed/complex feelings.
この問題は複雑で、一度に全部を説明するのは難しい。
This issue is complicated; it's hard to explain everything at once.
彼の気持ちは複雑で、喜びと不安が入り混じっているようだ。
His feelings are complicated — it seems joy and anxiety are mixed.
複雑な手続きのために、書類を何度も提出しなければならなかった。
Because of the complicated procedures, I had to submit the documents several times.