极其 is an adverb meaning 'extremely' or 'to an extraordinary degree'. It intensifies adjectives, verbs, or other adverbs—similar to English words like 'incredibly', 'exceptionally', or 'profoundly'. Though composed of two characters—极 (jí), meaning 'utmost' or 'extreme', and 其 (qí), a classical pronoun often used here as a grammatical intensifier—the phrase functions as a single unit and cannot be separated in modern usage.

This word carries a formal or literary tone and is common in written Chinese, news reports, academic writing, and formal speech. It’s stronger than very (很) and more emphatic than quite (相当) or fairly (比较). While it can modify many parts of speech, it never stands alone as a subject or object; it always modifies something else. Learners should note that it’s not used in casual spoken Chinese as frequently as superlatives like 特别 or 非常.