Neuron
Elongated cell that consists of a cell body containing nucleus (perikaryon) and processes.
Axon
Narrow, does not taper and has little endoplasmic reticulum
Dendrite
On the cell body, usually multiple in number, tapered shape, relatively short and contain large amounts of endoplasmic reticulum
Synapse
A connection between an axon and a target. That target could be another neuron or some external substance like muscle.