其中 (qí zhōng) is a prepositional phrase meaning 'among them' or 'within it'. It combines 其 (qí), a classical pronoun meaning 'its', 'his', 'her', or 'their' (used here as a demonstrative or possessive), and 中 (zhōng), meaning 'middle', 'inside', or 'among'. Together, they indicate inclusion or location within a previously mentioned group or thing. The phrase always refers back to something already introduced in context — never used in isolation.

其中 is common in both spoken and written Chinese, especially when specifying a subset of a larger set: animals in a zoo, items on a list, people in a group, or features within a system. It often appears after nouns or noun phrases and before verbs or descriptive clauses. While grammatically neutral, it carries a slightly formal or explanatory tone — more frequent in explanations, reports, or descriptions than in casual small talk.