在这些句子中，所有 be subject to 后面的行为或事件，实际上并未发生，只是有这种可能性。如果 to 后是法律条文，意思是受到法律条文约束，“要交税、要罚款” 也是有前提的，如果这些前提没有达到，那是不受影响或约束的。be subject to 的含义是：易受 ... 影响的（即英英释义）；屈服于 ... ；让步于 ...；取决于...，受到...支配，受到...约束，受到...管辖。我把句子翻译成汉语，你仔细体会。

Flights are subject to delay because of the fog. 由于大雾，航班可能延误。

Clothing purchases over $200 are subject to tax. 购买200美元以上的服装要纳税。

Anyone caught trespassing is subject to a $500 fine.任何人非法侵入都将被罚款500美元。

The firm is subject to state law. 该公司要受州法律约束。

The schedule is tentative and subject to change. 时间表是暂定的，可能会更改。

Prices are subject to change. 价格可能有变动。

英英释义，是从语言的内在含义中取其精华。在理解时，有些细微的词义要通过引申才能翻译出来，做到准确无误。

如果实在不好理解，我给网友一个好办法：由于主语“容易受到 to 后名词的影响”，这个名词带有动词意义，你可以把这个名词变成同源动词，然后变成被动，即：把 be subject to + 名词 变成这个被动形式：be likely to be done，用这个格式去理解句子意思吧。例如：

Flights are subject to delay because of the fog. = Flights are likely to be delayed because of the fog.

Clothing purchases over $200 are subject to tax. = Clothing purchases over $200 are likely to be taxed.

Anyone caught trespassing is subject to a $500 fine. = Anyone caught trespassing is likely to be fined $500.

The schedule is tentative and subject to change. = The schedule is tentative and is likely to be changed.

Prices are subject to change.= Prices are likely to be changed.