A connection between neurons, which is either continuous (in electrical synapses) or interrupted by a cleft (in chemical synapses), through which communication is established.
Neurotransmitters are used to cross the synaptic cleft to bind with post-synaptic receptors, and in certain cases retrograde messengers are passed back to the presynaptic cell.
The term is thought to have been coined by Sir Charles Scott Sherrington, an early pioneer in neuroscience and pathology.
See also neuroscience.