What are ganglia or ganglion?

Answer:
A ganglion is a mass of nerve tissue existing outside the central nervous system. (Dictionary.com) If you're using a textbook, there's usually a glossary in the back, which gives definitions.
First answer by Jdanielcross. Last edit by Jdanielcross. Contributor trust: 9 [recommend contributor recommended]. Question popularity: 4 [recommend question].