Is an earthworm a vertebrate or invertebratate if yes why?

Invertebrate. Earthworms are part of the rank 'Annelida' which translated (From french and eventually Laton) means "little ring". This term described how they are structured -rings or segments.

Quite simply a worm (earthworm) is an invertebrate (lacking vertebra/back bone).

Simple test, cut worm in half, does it have a spine? no? then its invertebrate!

I got this answer by searching 'invertebrate' on wikipedia then did a page search 'earthworm' :D