σύναψις

The Greek noun sýnapsis derives from synáptein, 'to clasp together,' 'to join,' 'to connect,' built from syn- (together, with) and háptein (to fasten, to clasp, to touch). Háptein and its derivatives appear throughout Greek in contexts of connection and contact — the word haptikos (able to touch) gave modern science the term 'haptic,' pertaining to the sense of touch. Synaptein was used in Greek for the joining of things in combat, the connection of an argument's premises, the link between a cause and its effect — always implying active fastening rather than passive adjacency. The two things being joined were understood to be genuinely touching each other.

The British neurophysiologist Charles Scott Sherrington coined 'synapse' in 1897 — specifically in a chapter he wrote for Michael Foster's Textbook of Physiology — to name the junction between nerve cells. This was a theoretical term before it was an observed structure: the existence of a gap between neurons was debated, with the 'neuron doctrine' (that neurons are discrete cells with gaps between them) competing against the 'reticular theory' (that neurons formed a continuous network). Sherrington chose synapse precisely because it described a joining that might involve a gap — the clasping of two hands is a connection that still involves two separate things. The debate was finally settled by electron microscopy in the 1950s, which revealed the synaptic cleft — typically 20–40 nanometers wide — confirming that the neurons clasp without truly merging.

The chemistry of synaptic transmission unfolded across the twentieth century: Otto Loewi's 1921 experiment proving chemical neurotransmission (he won the 1936 Nobel Prize), the identification of acetylcholine, dopamine, serotonin, glutamate, and dozens of other neurotransmitters, and the discovery that most psychiatric drugs work by modifying synaptic chemistry. The synapse is now understood as not just a passive junction but an active site of computation, plasticity, and memory formation — synaptic strength changes with use, which is the leading candidate mechanism for how the brain stores memories. Sherrington's clasping metaphor, borrowed from ancient Greek, named something more dynamic than any clasp: a conversation between cells.