polymerization (n.)

a substance built from a large number of simple molecules of the same kind, 1855, probably from German Polymere (Berzelius, 1830), from Greek polymeres "having many parts," from polys "many" (from PIE root *pele- (1) "to fill") + meros "part" (from PIE root *(s)mer- (2) "to get a share of something").