affectless 無動于衷的；
aimless 無目的的；
airless 新鮮空氣不足的'。
例句：
He dismissed the opinion polls as worthless.
他認為民意測驗毫無用處而不予考慮。
Training is worthless unless there is proof that it works.
訓練并無價值，除非證明其有效。
An agreement is worthless till our name is written with a pen.
除非用筆把我們的名字寫下來，否則協議毫無價值。