The affix kan comes after a word expressing a time or a cause or effect (of the disease) when an illness is denoted.,
The word काल means 'days' &c, and प्रयोजन means 'the cause (of disease) or its effect'. Thus द्वितीयेऽह्निभवः = द्वितीयको ज्वरः 'the fever which comes on the second day'. चतुर्थकः 'a fever which comes on the fourth day'. Similarly after a word denoting प्रयोजनः, as, विषपुष्पैर्जनितः = विषपुष्पको ज्वरः 'a fever caused by poisonous flowers'. So also काषपुष्पकः ॥ So also उष्णं कार्यमस्य = उष्णकः 'a fever producing heat', शीतको ज्वरः ॥
When 'illness' is not meant, then there is no affixing, as, द्वितीयो दिवसोऽस्य ॥ The word संज्ञा is to be read into this sutra from the next sutra. Therefore words द्वितीयकः &c are Names.,