当且仅当 當且僅當

    dāngqiějǐndāng

    1. Idiomif and only if

    一个数是偶数当且仅当它能被2整除。Yīge shǔ shì ǒushù dāngqiějǐndāng tā néng bèi 2 zhěngchú.A number is even if and only if it is divisible by 2.