As described in the Websters dictionary, Terrarium: a usually transparent enclosure for keeping or raising plants or usually small animals (as turtles) indoors. Vivarium: a terrarium used especially for small animals
Vivarium: an enclosure for keeping or raising and observing animals or plants indoors. Generally made up of 50 percent each water & land. Usually won't see any plastic plants in one of these setups. Check this site out: http://www.poison-frogs.nl/e03.html Terrarium: a vivarium without standing water, generally 10% or less water. Can also be any transparent more or less sealed enclosure. Ok, does that help the confusion?