Neurotransmitter
Etymology
A twentieth-century scientific compound: Greek "neuron" (nerve, originally sinew) plus "transmitter," from Latin "transmittere" (to send across). The concept of chemical signaling between neurons was established experimentally in the early 1900s.
noun · /NOOR-oh-tranz-MIT-er/
A chemical messenger that carries a signal across the synapse from one nerve cell to another.
What it names
The molecular unit of communication in the nervous system, the substance that turns an electrical impulse into a message the next cell can receive.
Example
Many antidepressants work by changing how long a neurotransmitter like serotonin lingers in the synapse.
Related idea
Contrast with a hormone, which is also a chemical messenger but travels through the bloodstream to distant targets; a neurotransmitter acts locally and almost instantly across a tiny gap between two cells.