In denoting the agent, when reciprocity of action is to be expressed, the affixes of the ātmanepada are employed.,
The active or कर्तृवाच्य verbs when denoting reciprocal action are atmanepadi. As, व्यतिपचन्ते, 'they cook for each other,' व्यतिलुनते 'he performs cutting of wood which was the appropriate office of another.'
The words \reciprocity or interchange of action\ of this sutra govern and are understood in the two following sutras also.
The word karma in the sutra means action and not the technical 'karma' meaning 'object' and the word vyatihara means reciprocity or interchange. When an action which was appropriate to one person is performed by another, whose duty it was not, that is called 'interchange of action.' When such interchange is not meant Paras. is used. As लुनन्ति 'they cut.' The word kartari here is used for the sake of the subsequent aphorism 1.3.78, which see.,