define chemistry between two people
In the context of relationships, chemistry is a simple emotion that two people get when they share a special connection. It is not necessarily sexual. It is the impulse making one think I need to see this [other] person again - that feeling of we click.
Chemistry is the study of matter, its properties, how and why substances combine or separate to form other substances, and how substances interact with energy. Many people think of chemists as being white-coated scientists mixing strange liquids in a laboratory, but the truth is we are all chemists.