替: on behalf of, for (someone)
【四16】介词 / prepositions
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
替 + person + verb: you do something in someone's place or on their behalf. 我替你去 (I'll go instead of you), 请替我向他问好 (please give him my regards for me). The 替 + person phrase goes before the verb, like 给 or 对.
With a verb of feeling, 替 names the person on whose account you feel it: 我替你高兴 (I'm happy for you), 别替我担心 (don't worry about me).
Do not mix it up with 给 and 帮. 给你做饭: I cook a meal for you (you are the one who receives it). 替你做饭: I cook in your place (it was your turn, or you can't). 帮你做饭: I help you cook (we do it together). Neutral register, spoken and written.
Examples
我替你去。
Wǒ tì nǐ qù.I'll go instead of you.
我今天不舒服，你能替我上班吗？
Wǒ jīntiān bù shūfu, nǐ néng tì wǒ shàngbān ma?I'm not feeling well today. Can you cover my shift for me?
请替我向你妈妈问好。
Qǐng tì wǒ xiàng nǐ māma wènhǎo.Please give my regards to your mum for me.
你别替我担心，我自己能解决。
Nǐ bié tì wǒ dānxīn, wǒ zìjǐ néng jiějué.Don't worry about me, I can sort it out myself.
听说你找到了新工作，我真替你高兴！
Tīngshuō nǐ zhǎodào le xīn gōngzuò, wǒ zhēn tì nǐ gāoxìng!I hear you found a new job. I'm really happy for you!
我妈妈不会用手机，我替她在网上订了机票。
Wǒ māma bú huì yòng shǒujī, wǒ tì tā zài wǎngshang dìng le jīpiào.My mum can't use a smartphone, so I booked her plane ticket online for her.
Common mistakes
✗ 请替我一个忙 → ✓ 请帮我一个忙 (a favour is asked with 帮; 替 must always be followed by a verb).
✗ 我给你很高兴 → ✓ 我替你高兴 (being happy for someone takes 替, not 给).
✗ 我做饭替你 → ✓ 我替你做饭 (替 + person goes before the verb).