Co-verbs are a group of verbs that often act as prepositions in a clause with another verb, though they can act as verbs in their own right (prepositional constructions I, p. 155).

Amongst them are: -

Zai    ‘to be at, be in, at, in, on’

            He is in China   他在中

            He studies at the Foreign Languages Institute   他在外语学学习

Gei    ‘to, for (for indirect objects), to give to’

            He gives me books  

            He introduced me to his friend   我介他的朋友

Yong    ‘by means of, to use’

            He is using a Chinese dictionary   他用汉语词典

            He reads the newspaper with [the help of]a dictionary   他用典看


Other co-verbs:

Ti    ‘for, as a substitute for’

            He is taking my place   他替我

            I am writing a letter for my mother   我替我妈妈写信

Some co-verbs are almost always used in prepositional phrases, and only usually act as verbs in their own right with complements attached.

Dui    ‘Concerning, vis-a-vis, to be in front of , facing something/one’

            He was facing the dormitory   着宿舍

            He is very good to students   对学生很好

Gen    ‘in company with, to follow’

            I follow my students to the Institute  我跟着我的

            I am going to the shops with my students   我跟我的生去商店

NB all co-verb constructions will come before the main verb in the way that prepositional or adverbial phrases come before the verbs they modify.