Serial-order of substances;
the principle of the structure of the substance and its order. E.g.-
Pūrvānupūrvī, Paścānupūrvī, Anānupūrvī.
pūrvvasya paścādannpūrvaṃ tasya bhāva iti... tasmādamipūrvabhāvaḥ ānupūrvī anukramo'nuparipātīti paryāyaḥ, tryādivastusaṃhatiriti bhāvaḥ.
(Anu 100 HāVṛ p.30)