替 vs 代

Both 替 (tì) and 代 (dài) can mean "to replace" or "on behalf of," but they differ in usage, grammar, and nuance. Here’s a detailed breakdown:

1. 替 (tì) – "To Replace" (Informal, Temporary, or Emotional)

Usage:

Temporary Replacement (Daily Life, Informal)

• Used for short-term, informal substitutions (e.g., taking someone’s place temporarily).
• Often implies helping or doing a favor.

Examples:

• 我今天生病了，你能替我去开会吗？ (Wǒ jīntiān shēngbìng le, nǐ néng tì wǒ qù kāihuì ma?)
  → "I’m sick today. Can you go to the meeting for me?" (Temporary help.)
• 他请假了，我替他值班。
  (Tā qǐngjià le, wǒ tì tā zhíbān.)
  → "He’s on leave, so I’m covering his shift."

Emotional/Personal Context

• Often used when expressing concern, worry, or happiness for someone.

Examples:

• 看到他成功，我们都替他高兴。
  (Kàn dào tā chénggōng, wǒmen dōu tì tā gāoxìng.)
  → "Seeing his success, we’re all happy for him."
• 别替我担心，我没事。 (Bié tì wǒ dānxīn, wǒ méishì.)
  → "Don’t worry about me; I’m fine."

Key Points:
✔ Temporary/informal replacement (helping someone).
✔ Often used in emotional contexts (替 + someone + emotion).
✔ Cannot form compound words like 代 can.

2. 代 (dài) – "To Replace" (Formal, Official, or Long-Term)

Usage:

Formal/Official Replacement

• Used for official, long-term, or professional substitutions.
• Often seen in job titles, formal roles, or technical terms.

Examples:

• 张经理今天不在，我代他签字。
  (Zhāng jīnglǐ jīntiān bù zài, wǒ dài tā qiānzì.)
  → "Manager Zhang isn’t here today; I’ll sign on his behalf." (Official duty.)
• 他是我们的代课老师。
  (Tā shì wǒmen de dàikè lǎoshī.)
  → "He’s our substitute teacher." (Formal role.)

Compound Words (代 + Noun)

• Forms many fixed terms (e.g., 代表 dàibiǎo "representative," 代理 dàilǐ "agent").

Examples:

• 他是公司的代表。 (Tā shì gōngsī de dàibiǎo.)
  → "He’s the company’s representative."
• 这个软件是我的代理。 (Zhè ruǎnjiàn shì wǒ de dàilǐ.)
  → "This software is my agent."

Historical/Generational Replacement

• Used for generational shifts (e.g., "next generation").

Examples:

• 新一代的科技正在改变世界。
  (Xīn yī dài de kējì zhèngzài gǎibiàn shìjiè.)
  → "The new generation of technology is changing the world."

Key Points:
✔ Formal/long-term replacement (official roles).
✔ Forms compound words (代表, 代理, 代课).
✔ Used for generational changes.

3. Key Differences

Final Summary

Use 替 (tì) for:
✔ Temporary/informal replacements (helping someone).
✔ Emotional contexts (替 + someone + emotion).

Use 代 (dài) for:
✔ Formal/official replacements (job roles, duties).
✔ Compound words (代表, 代理, 代课).
✔ Generational changes (新一代).