In certain circumstances zài can be omitted from the locative expression. Grammatically, a noun or noun phrase followed by a locative particle is still a noun phrase. For instance, zhuōzi shàng can be regarded as short for zhuōzi shàngmiàn, meaning something like "the table's top". Consequently, the locative expression without zài can be used in places where a noun phrase would be expected – for instance, as a modifier of another noun using de (), or as the object of a different preposition, such as cóng (, "from"). The version with zài, on the other hand, plays an adverbial role. However, zài is usually omitted when the locative expression begins a sentence with the ergative structure, where the expression, though having an adverbial function, can be seen as filling the subject or noun role in the sentence. For examples, see sentence structure section.
