perfectly mobile component
perfectly mobile component[′pər·fik·lē ′mō·bəl kəm′pō·nənt]
A component whose quantity in a system is determined by its externally imposed chemical potential rather than by its initial quantity in the system. Also known as boundary value component.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.