摘要：I should add that these reports are as yet unconfirmed. (我还要补充一点，这些报道尚未得到证实。)[剑桥高级学者辞典]

as yet是formal表达，用于语义否定的句子，含义为“到目前为止，迄今为止，到此为止”。

时间截止点通常是“当下、目前”，主干句的时态是现在时或现在完成时，如

【例句1】As yet it is not known whether the crash was the result of an accident. (目前尚不清楚这次撞车是否是事故造成的。) [柯林斯高级学者辞典]

【例句2】There's no sign as yet that the economy is recovering.（目前还没有迹象表明经济正在复苏。）[剑桥高级学者辞典]

【例句3】I should add that these reports are as yet unconfirmed. (我还要补充一点，这些报道尚未得到证实。)[剑桥高级学者辞典]

【例句4】We have not as yet received a response. (我们还没有收到答复。)[柯林斯高级学者辞典]

【例句5】We haven't needed extra staff as yet, but we may in the future. （我们还不需要额外的员工，但将来可能会。）[剑桥高级学者辞典]

如果主干句的时态是过去时或过去完成时，则截止时间是与主干句关联的过去时刻，如

【例句6】As yet little was known of the causes of the disease. (到此为止，人们对这种疾病的病因知之甚少。)[牛津高级学者辞典]

【例句7】No ambulances had as yet managed to get across the river. (到此为止，还没有救护车能过得了河。)[剑桥高级学者辞典]

【例句8】We've had no word from Colin as yet. （到此为止，我们还没有收到科林的消息。）[朗文当代英语词典]

下句的主干是将来时，但as yet是untitled的时间状语，后者时间应为“说话当下”，

【例句9】In March he'll release his as yet untitled fifth album. （3月，他将发行尚未命名的第五张专辑。）[剑桥高级学者辞典]

讨论：

1. as yet可以在句首、助动词和主动词之间和句尾，“到此为止”的强调感依次减弱。

2. as yet有“将来可能发生的心理期盼”。

3. yet的词源比较乱。按wordsense, yet可追到原始欧洲语*h₂yew-，有long time之义。按etymonline，yet有in continuance of a former state。两者合起来，大概有“经过长时间的状态持续，[从而有点心烦]”。

来源：坐北朝南