groundless

形容词 groundless:

1. without a basis in reason or fact
   同义词：baseless, idle, unfounded, unwarranted, wild

1. Facts have proved these worries groundless.
   事实证明，这些忧虑是没有根据的。
2. Of course, these implications would sly and groundless, and the opposition would realize it. But the voters might not. They would say where there's smoke there's fire.
   当然这些暗示是狡诈的，毫无根据的，反对派懂得这点。但选民不一定懂得，他们会说无风不起浪。

ground.less

adj.（形容词）
Having no ground or foundation; unsubstantiated:
毫无根据的：没有根据或基础的；缺乏根据的：
例句：
groundless optimism.See Synonyms at baseless
毫无根据的乐观参见 baseless

【引伸】
ground.lessly
adv.（副词）
ground.lessness
n.（名词）