One of the mysteries of the English language finally explained.
Any extracellular or intracellular molecule (e.g. a hormone, neurotransmitter, second messenger, etc.), released in response to a stimulus that promotes a particular reaction in a cell, or behaviour in an organism; especially such a molecule involved in cell-to-cell communication.
1960s; earliest use found in Journal Insect Physiology.
In this article we explore how to impress employers with a spot-on CV.