AbstractRapid and precise neuronal communication is enabled through a highly synchronous release of signaling molecules neurotransmitters into the synaptic cleft within just milliseconds of the action potential. Yet neurotransmitter release lacks a theoretical framework that is both phenomenologically accurate and mechanistically realistic. Here, we formulate an analytic theory of the action-potential-triggered neurotransmitter release at a chemical synapse. The theory captures general principles of synaptic transmission while generating concrete predictions for particular synapses. A universal scaling in synaptic transmission is established, and demonstrated through a collapse of experimental data from different synapses onto a universal curve. The theory shows how key characteristics of synaptic function – plasticity, fidelity, and efficacy – emerge from molecular mechanisms of neurotransmitter release machinery.