Mood Adverb: 乃
语气副词：乃
Use the literary copula 乃 to make formal or emphatic statements of identity
乃 functions as a literary equivalent of 是 (to be), linking a subject to its identity or classification. It is used in formal, literary, or proverbial language.
乃 is a classical Chinese word that survives in modern set phrases and formal writing. It sounds very literary and should not be used in casual conversation unless for stylistic or humorous effect.
Lesson Targets
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Podcast: Mood Adverb: 乃 (语气副词：乃)
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Understanding 语气副词：乃
乃 is one of the most recognizable words from classical Chinese (文言文). In its most common modern usage, it functions like 是 (to be), but with a formal, elevated, or proverbial tone. When you hear 失败乃成功之母 (Failure is the mother of success), the 乃 gives the proverb its weight and authority — using 是 instead would sound flat. In modern Chinese, 乃 appears in set phrases, formal writing, historical texts, and idiomatic sayings. It is not used in casual conversation. Learning 乃 is essential for reading Chinese literature, understanding proverbs, and appreciating the connection between classical and modern Chinese.
Key Points
- 乃 (nǎi) = literary "is / to be" — equivalent of 是 in formal or classical contexts.
- Primarily found in proverbs, set phrases, formal writing, and classical texts.
- Gives statements an authoritative, timeless quality.
- Not used in casual spoken Chinese — sounds overly literary.
- Also means "then / thereupon" in classical narrative contexts (a secondary meaning).
- Common in famous sayings: 失败乃成功之母.
- Recognizing 乃 is essential for reading classical Chinese and literary texts.
Classical Chinese (文言文) was the written standard for over two thousand years. Words like 乃 bridge modern learners to this vast literary heritage. Many Chinese proverbs and formal expressions preserve 乃 as a connection to that tradition.
Key Vocabulary
Example Sentences
《红楼梦》乃古代小说的杰出代表。
Dream of the Red Chamber is an outstanding representative of classical novels.
失败乃成功之母。
Failure is the mother of success.
One of the most famous Chinese proverbs
民以食为天，饮食乃人生大事。
Food is heaven for the people — eating is a great matter of life.
诚信乃做人之本。
Integrity is the foundation of being a good person.
此乃千载难逢的好机会。
This is a once-in-a-thousand-years opportunity.
教育乃国家发展的根本。
Education is the foundation of national development.
Common Mistakes
Using 乃 in casual self-introductions sounds absurdly literary — like speaking Shakespearean English. Use 是 for everyday statements.
乃 links a subject to a noun or noun phrase — not to adjective predicates with 很. If using 乃, the entire sentence should match its literary register.
The negative of 乃 is not 乃不是 — use 非 or 并非 in literary Chinese, or 不是 in modern Chinese.
Practice Exercises
Tips & Tricks
Think of 乃 as the Chinese equivalent of "thou art" — grand, literary, and not for daily chat.
Memorize the proverb 失败乃成功之母 — it is one of the most quoted sayings in Chinese.
When reading classical Chinese, 乃 is everywhere. Recognizing it instantly unlocks many texts.
For fun: using 乃 in casual speech creates a humorous, dramatically formal effect — like speaking in movie dialogue.
Homework
Write three formal statements using 乃: (1) a statement about the importance of health, (2) a statement praising a famous work of art or literature, and (3) a proverb-style sentence about friendship or knowledge. Then rewrite each using 是 and note the difference in tone.