Re: what is or are the differences between poison, venom and toxin?

toxin - any substance that can cause harm
poison - a toxin that causes its effect through ingestion or absorbtion
venom - a toxin that causes its effect through administration via a 
specialised delivery system 

A good example is tetrodotoxin, a toxin that can be a poison or a venom.   
It is a poison in pufferfish, causing its effect when tissues from this 
fish are eaten.  It is a venom in the blue-ringed octopus, being stored in 
salviary glands and delivered into a wound caused by the beak of the 
octopus.

Thus, snakes are venomous since the toxin is delivered via specialised 
apparatus while poison arrow frogs are poisonous since the toxin is 
absorbed.

Cheers,
Bryan

International Venom & Toxin Database http://www.uq.edu.au/~ddbfry/index.html