There are many similarities between these two structures, the main differences are: Neuromuscular junction (NMJ) is between a neurone and a muscle. A synapse is neurone-neurone.Neuromuscular junctions are only ever excitatory whereas a synapse can be excitatory or inhibitory. Neuromuscular junctions use T-tubules to carry the signal quickly, synapses don't.
Similarities:They both use acetylcholine as a neurotransmitter and therefore acetylcholinesterase to prevent constant impulses.They are both triggered by action potentials on the pre-synaptic membrane.Depolarisation occurs on the post-synaptic membrane to cause a response