Upadāna Kāraṇam — The Material Cause
Upadāna kāraṇam (Sanskrit: upadāna = material/substance + kāraṇam = cause; 'material cause' or 'the cause from which something is made') is one of the three classical Vedāntic causes (tri-kāraṇam) — the stuff from which something is made, as opposed to the agent who makes it (nimitta kāraṇam) or the instrumental causes that assist (sahakāri kāraṇam).
Standard Analogies: The clay from which a pot is made is the upadāna kāraṇam of the pot (the potter is the nimitta; the wheel and water are sahakāri). Gold is the upadāna of a gold ornament. These analogies help explain how the cause persists within the effect.
In Viśiṣṭādvaita: Rāmānuja's great claim is that Brahman (Bhagavān Nārāyaṇa) is both the nimitta and the upadāna kāraṇam of the universe. 'Brahman, with cit and acit as His body (śarīra), transforms into the universe while remaining unchanged in essential nature. The cit-acit-Īśvara complex is the upadāna.' This is distinct from Advaita (where Brahman alone is real) and Sāṅkhya (where Prakṛti alone is the upadāna).
Why This Matters: Bhagavān being the upadāna means creation is not from nothing (ex nihilo) nor from an independent substance — the universe is Bhagavān's own body. This grounds Śrī Vaiṣṇava body-soul metaphysics (śarīra-śarīrī bhāva).