当worth用在系词之后时，现代英语常见的用法是 be worth +名词、代词或动名词。但曾几何时历史上的形容词worth作表语，由于其语义不完整，需要of介词短语补足其语义，用法是be worth of +名词、代词或动名词，即用法类似于be fond of。换句话说，表语位置的形容词worth 和形容词 fond 一样语义不完整，需要of介词短语补足其语义。随着时代的变迁和语言的变化，worth作表语时后面的介词of逐渐脱落了，形成了表语形容词直接后接名词性结构的现象，看上去就好像是worth是介词似的。其实这个名词性结构是脱落了的介词of的宾语。有的词典根据历史原因，仍然把这个worth分析为形容词，有的词典根据现代用法把worth分析为介词，有的词典采用折衷的方法，说worth是形容词，但用如介词，即后面必须接名词性结构。这就是worth作为形容词做表语为什么会后接名词的原因。我们偶尔还会见到of不省略的句子，这就是早期用法的残留现象。例如语料库例句：

When we love, we evaporate our fear, which is the exact thing a child of God IS worth of: Love.

...  they have nothing that is worth of interest to Mexican or north American authorities.

Believe me it is worth of a try, it is completely free and useful.

The zeal held by geomancy practitioners in Korea for improving the local landscape is worth of comparing with the notion, held by medieval monastic monks in Europe, that humanity partners with God to improve creation the earth's environment.

You are not going to be testing each of your individual you cross in the street to see if they all are worth of moral consideration.

People need to prove themselves first, so to speak, to show they are worth of someone's time and energy (not to mention emotions).

They offer no solutions to solve problems that are worth of our support.