What is the difference between 互相 and 彼此

Question

I was told they were interchangeable except in few cases. What are they?

Answer 1

Yes and no.

互相 - one another; each other; mutual; mutually.

彼此 - one another; each other.

Above are interpretations from the dictionary, the meanings seem to overlap, but not exactly.

• 互相 should mean "one another mutually provide some favor in return" - 你我互相幫助 (You help me, and I help you).

• 彼此 should mean "you and I" or "each other" - 彼此之間 (Between you and me); 不分彼此 (we are equal, nothing divides us).

However, they are interchangeable as in the sentence below:

• 兄弟姐妹間要互相扶助

• 兄弟姐妹間要彼此扶助

In the sentences above, both mean "each other", or "one another" - Siblings shall help each other (one another).

Also note that the two can work together in a sentence:

• 你們要"彼此互相"幫助 - You shall (mutually) help each other. Note that the sequence of 彼此互相 should not be reversed.

Answer 2

What I understand as a native speaker is that,

互相 focuses on the relationship between 2 or more objects,

彼此 focuses on the "both sides", 那个和这个, that and this.

Answer 3

彼此 is more like a noun when 互相 is more like an adverb in a sentence.

Including the example from SE12938683, terms below never use 互相 simply because 互相 cannot become things/objects.

不分彼此 (No difference between you and me/he/she.)
彼此之間 (In between A and B. 彼此 acts as a subject.)
彼此要相親相愛 (A and B should cherish and love each other. Here also starts as a subject, meaning you and he/her, or this and that.)

Answer 4

In my understanding, 彼此 focuses on the two parties, you and me, while 互相 focuses on the relationship and it's mutual.

Answer 5

They are not interchangeable in most cases. “彼此” is sort of literary and only used with persons.

Edit: “彼此之间” would be an exception, I used it for two items today...