Basic Uniform Commercial Code
"Accession" means goods that are physically united with other goods in such a manner that the identity of the original goods is not lost.
Copyright, The American Law Institute
E.g., like tires being put on a car.
Security interests remain attached and perfected in an accession. UCC § 9-335(a)–(b).
However, security interests in accessions are subordinate to security interests perfected by certificate of title. UCC § 9-335(d).