互相 + 動詞（互いに）

Two partners check each other’s drafts

• Mei checks Arun’s draft and Arun checks Mei’s. You can say they他们tā meneach other互相hùxiānghelp帮助bāngzhù。 — “They help each other.” The relationship goes in both directions.
• If only Mei helps Arun, say old variant of 梅梅méihelp帮助bāngzhùAalen, town in Germany阿伦ā lún。 That one-way account does not establish mutual help.

Place each other互相hùxiāng before the reciprocal action

• Use participants + each other互相hùxiāng + verb phrase: we我们wǒmeneach other互相hùxiānghelp帮助bāngzhù / they他们tā meneach other互相hùxiāngto see看kàn(completed / change)了lea glance一眼yī yǎn。 State or recover the people involved from context.
• I / me我wǒwith / and跟gēnhe / him他tāeach other互相hùxiānghelp帮助bāngzhù includes both participants. The word I / me我wǒ does not make the sentence wrong when with / and跟gēnhe / him他tā supplies the other participant.

we我们wǒmenshould应该yīnggāieach other互相hùxiānghelp帮助bāngzhù。

Reciprocity does not mean equal amounts

• In a group, each other互相hùxiāngto learn学习xué xí can mean people learn from one another. It need not describe exactly two people or every possible pair doing the same amount.
• Mei may help with diagrams while Arun helps with language. The actions support one another even though the contributions differ.

Distinguish each other互相hùxiāng from all / both都dōu

• we我们wǒmenall / both都dōuhelp帮助bāngzhùteacher老师lǎo shī says every person in the relevant group helps the teacher. It does not say they help one another.
• we我们wǒmeneach other互相hùxiānghelp帮助bāngzhù makes the participants both helpers and recipients within the relationship. Read who acts on whom.

Check the action and the participants

• A completed mutual glance is possible: they他们tā meneach other互相hùxiāngto see看kàn(completed / change)了lea glance一眼yī yǎn。 Reciprocity does not require a repeated habit or a long duration.
• Do not add each other互相hùxiāng to an unrelated one-person activity without a reciprocal partner. Describe the actual relationship rather than using it as a general word for cooperation.

Trace the relationship before translating

• For two partners, draw A → B and B → A to test mutual help. A → teacher and B → teacher instead represents both helping the same third person.
• For a larger group, use the stated interaction evidence. each other互相hùxiāng signals reciprocity, not a guaranteed equal contribution from every person.

Read the full reference: HSK 5 grammar — Adverbs.