给 vs 为 (to/for vs for the sake of)

A gift and a sacrifice

• Your mother works late every night to support the family.
• Mum妈妈mā main order to为了wèi lewe我们wǒ menevery day每天měi tiānto work工作gōng zuòto / arrive到dàodegree / adjective linker很hěnevening晚wǎn，I我wǒwant / think / miss想xiǎngfor给gěishe / her她tābuy买mǎi一份yī fèngift礼物lǐ wù。 — "Mum works late every day for us; I want to buy her a present."

for给gěi = to / for (a recipient)

• for给gěi + person + verb = do something for / to someone who receives it: for给gěishe / her她tābuy买mǎigift礼物lǐ wù, for给gěiI我wǒto make a telephone call打电话dǎ diàn huà, for给gěiyou你nǐto introduce (sb to sb)介绍jiè shào.
• The person gets the thing or the service.

I我wǒfor给gěiMum妈妈mā mabuy买mǎi了lea bunch of一束yí shùflowers花huā。

for为wèi = for the sake of, because of

• for为wèi + person / cause + verb = for the sake of, on behalf of: for为wèieveryone大家dà jiāserve服务fú wù, for为wèiyou你nǐare happy高兴gāo xìng, for为wèichild孩子hái zianxious担心dān xīn.
• for为wèi often goes with feelings and effort.

we我们wǒ menall都dōufor为wèiyou你nǐare happy高兴gāo xìng。

Receiving versus caring

Where both work

• "Do something for someone" can sometimes take either: for给gěi / for为wèieveryone大家dà jiāto prepare a meal做饭zuò fàn.
• for给gěi is more everyday; for为wèi sounds more formal or dedicated: for为wèithe people人民rén mínserve服务fú wù — "serve the people".

for为wèithe people人民rén mínserve服务fú wù。

Recap

Read the full reference: HSK 5 grammar — Comparing similar prepositions.