The Compendium of Caraka 3.6.11

3.6.11

tatrānubandhyānubandhakṛto viśeṣaḥ---svatantre vyaktaliṅgo yathoktasamutthānapraśamo bhavatyanubandhyaḥ, tadviparītalakṣaṇastvanubandhaḥ/

In that context, the distinction made by primary and secondary is: that which is independent, with manifest symptoms, whose onset and alleviation are as described, is primary; while that which has the opposite characteristics is secondary.