The Nyāya-Vaiśeṣika philosophy recognizes two kinds of relations: saṁyoga or conjunction and samavāya or inherence. Conjunction is a temporary phenomenon which will come into existence when two things—like two balls moving from opposite directions—meet. Since it comes into existence (siddha) when the two are united (yuta), it is called ‘yutasiddha.’
However, in the case of samavāya, as distinct from saṁyoga, the relationship is permanent since one inheres in the other. For instance, the whole inheres in the parts (as cloth in its threads), a quality or an action inheres in a substance (as redness in the rose, motion in the moving ball) or the universal inheres in the individuals (as manhood in men). Here, the two (e.g., cloth and threads or redness and rose) are related without conjunction. This relation exists (siddha) eventhough there is no conjunction (ayuta) between the entities. Hence it is called ‘ayuta-siddha.’
Samavāya is a relationship of the ‘ayutasiddha’ type.
See also SAMAVĀYA.