synaptic vesicle Wikipedia:Synaptic_vesicle docked vesicle cellular_component A secretory organelle, typically 50 nm in diameter, of presynaptic nerve terminals; accumulates in high concentrations of neurotransmitters and secretes these into the synaptic cleft by fusion with the 'active zone' of the presynaptic plasma membrane. NIF_Subcellular:sao1071221672 This term should not be confused with GO:0097547 'synaptic vesicle protein transport vesicle'. STVs and synaptic vesicles differ both functionally and morphologically. Functionally, STVs are transport vesicles that deliver synaptic vesicle proteins to synapses, while synaptic vesicles are responsible for transmitter release at synapses. Morphologically, synaptic vesicles are very homogeneous, while STVs are very heterogeneous in size and shape. STVs might be a precursor for synaptic vesicles. GO:0008021 organelle