1. The science of the composition, structure, properties, and reactions of matter, especially of atomic and molecular systems.
2. The composition, structure, properties, and reactions of a substance.
3. The elements of a complex entity and their dynamic interrelation: "Now that they had a leader, a restless chemistry possessed the group" (John Updike).
4. Mutual attraction or sympathy; rapport: The chemistry was good between the partners.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.