affectless 无动于衷的；
aimless 无目的的；
airless 新鲜空气不足的'。
例句：
He dismissed the opinion polls as worthless.
他认为民意测验毫无用处而不予考虑。
Training is worthless unless there is proof that it works.
训练并无价值，除非证明其有效。
An agreement is worthless till our name is written with a pen.
除非用笔把我们的名字写下来，否则协议毫无价值。