The function of B˘ıc˘ı (彼此) is similar to the English reciprocal pronoun "each other." B˘ıc˘ı (彼此) are two morphemes that are demonstratives in classical Chinese and occur most frequently in the adverb position.
→他們彼此尊重 (t¯a-men bi-ci z¯unzh`ong/ They respect each other.)
Also, bǐcǐ (彼此) can be easily replaced by a similar reciprocal adverb hùxiāng (互相).