If you forget to mention a prefix in any step, your expression will return nothing-an error for which it's difficult to track the cause.

如果有任何一个步骤忘记使用这个前缀，那么表达式不会返回任何内容，并且很难搞清楚究竟是哪一步出的错。

youdao

The XPath expression used to define the XML part to search in does not contain the namespace prefix — the fully qualified element name (QName), in other words.

用来定义要搜索的XML部分的XPath表达式没有包含名称空间前缀——换句话说，没有包含完全限定的元素名称(QName)。

youdao

These patterns of gene expression are governed by the cellular material - the epigenome - that sits on top of the genome, just outside it (hence the prefix epi -, which means above).

基因表达模式(patterns of gene expression)受细胞物质外基因所控。外基因，高于基因，通俗点说，基因之外(前缀epi -，意即上面)。

youdao